* Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
@ 2026-04-15 0:52 ` Edward Adam Davis
2026-04-15 4:10 ` syzbot
2026-04-15 8:29 ` [PATCH] hfsplus: Add a sanity check for catalog btree node size Edward Adam Davis
` (6 subsequent siblings)
7 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-15 0:52 UTC (permalink / raw)
To: syzbot+217eb327242d08197efb; +Cc: linux-kernel, syzkaller-bugs
#syz test
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index 250a226336ea..56a046ba4d54 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -576,7 +576,10 @@ struct hfs_bnode *hfs_bnode_find(struct hfs_btree *tree, u32 num)
goto node_error;
}
- rec_off = tree->node_size - 2;
+ if (tree->node_size < 2)
+ goto node_error;
+ else
+ rec_off = tree->node_size - 2;
off = hfs_bnode_read_u16(node, rec_off);
if (off != sizeof(struct hfs_bnode_desc))
goto node_error;
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find
2026-04-15 0:52 ` Edward Adam Davis
@ 2026-04-15 4:10 ` syzbot
0 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-04-15 4:10 UTC (permalink / raw)
To: eadavis, linux-kernel, syzkaller-bugs
Hello,
syzbot has tested the proposed patch but the reproducer is still triggering an issue:
KMSAN: uninit-value in irqentry_exit_to_kernel_mode_preempt
=====================================================
BUG: KMSAN: uninit-value in irqentry_exit_to_kernel_mode_preempt+0xe3/0x120 include/linux/irq-entry-common.h:472
irqentry_exit_to_kernel_mode_preempt+0xe3/0x120 include/linux/irq-entry-common.h:472
irqentry_exit_to_kernel_mode include/linux/irq-entry-common.h:547 [inline]
irqentry_exit+0x77/0x710 kernel/entry/common.c:164
sysvec_apic_timer_interrupt+0x52/0x90 arch/x86/kernel/apic/apic.c:1061
asm_sysvec_apic_timer_interrupt+0x1f/0x30 arch/x86/include/asm/idtentry.h:697
smap_save mm/kmsan/instrumentation.c:93 [inline]
get_shadow_origin_ptr mm/kmsan/instrumentation.c:35 [inline]
__msan_metadata_ptr_for_load_4+0x11/0x40 mm/kmsan/instrumentation.c:93
do_csum lib/checksum.c:64 [inline]
ip_fast_csum+0x1e6/0x3f0 lib/checksum.c:99
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:842 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
nsim_dev_trap_report_work+0x8c0/0x1430 drivers/net/netdevsim/dev.c:922
process_one_work kernel/workqueue.c:3288 [inline]
process_scheduled_works+0xb65/0x1e40 kernel/workqueue.c:3371
worker_thread+0xee4/0x1590 kernel/workqueue.c:3452
kthread+0x53f/0x600 kernel/kthread.c:436
ret_from_fork+0x20f/0x8d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Uninit was created at:
slab_post_alloc_hook mm/slub.c:4545 [inline]
slab_alloc_node mm/slub.c:4866 [inline]
__do_kmalloc_node mm/slub.c:5259 [inline]
__kmalloc_node_track_caller_noprof+0x4f6/0x1750 mm/slub.c:5368
kmalloc_reserve net/core/skbuff.c:635 [inline]
__alloc_skb+0x90d/0x1190 net/core/skbuff.c:713
alloc_skb include/linux/skbuff.h:1383 [inline]
nsim_dev_trap_skb_build drivers/net/netdevsim/dev.c:819 [inline]
nsim_dev_trap_report drivers/net/netdevsim/dev.c:876 [inline]
nsim_dev_trap_report_work+0x3f2/0x1430 drivers/net/netdevsim/dev.c:922
process_one_work kernel/workqueue.c:3288 [inline]
process_scheduled_works+0xb65/0x1e40 kernel/workqueue.c:3371
worker_thread+0xee4/0x1590 kernel/workqueue.c:3452
kthread+0x53f/0x600 kernel/kthread.c:436
ret_from_fork+0x20f/0x8d0 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
CPU: 0 UID: 0 PID: 134 Comm: kworker/u8:6 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/18/2026
Workqueue: events_unbound nsim_dev_trap_report_work
=====================================================
Tested on:
commit: 91a4855d Merge tag 'net-next-7.1' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14f418ce580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9f67daa5723e634c
dashboard link: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
patch: https://syzkaller.appspot.com/x/patch.diff?x=170efb02580000
^ permalink raw reply [flat|nested] 18+ messages in thread
* [PATCH] hfsplus: Add a sanity check for catalog btree node size
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
2026-04-15 0:52 ` Edward Adam Davis
@ 2026-04-15 8:29 ` Edward Adam Davis
2026-04-15 22:32 ` Viacheslav Dubeyko
2026-04-17 10:12 ` Forwarded: [PATCH] hfsplus: initialize data in hfs_bnode_read_u16 and syzbot
` (5 subsequent siblings)
7 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-15 8:29 UTC (permalink / raw)
To: syzbot+217eb327242d08197efb
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzkaller-bugs
Syzbot reported a uninit-value bug in [1], during the file system mounting
process, specifically while loading the catalog, a corrupted node_size
value of 1 caused the rec_off argument passed to hfs_bnode_read_u16()
(within hfs_bnode_find()) to be excessively large. Consequently, the
function failed to return a valid value to initialize the off variable,
triggering the bug [1].
To prevent similar issues, a check for the catalog btree node size has
been added within the hfsplus_btree_open() function.
[1]
BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
fs/hfsplus/btree.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 761c74ccd653..61050ffe425e 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -337,6 +337,11 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
pr_err("invalid catalog btree flag\n");
goto fail_page;
}
+ if (tree->node_size < 2) {
+ pr_err("invalid catalog btree node size %u\n",
+ tree->node_size);
+ goto fail_page;
+ }
if (test_bit(HFSPLUS_SB_HFSX, &HFSPLUS_SB(sb)->flags) &&
(head->key_type == HFSPLUS_KEY_BINARY))
--
2.43.0
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [PATCH] hfsplus: Add a sanity check for catalog btree node size
2026-04-15 8:29 ` [PATCH] hfsplus: Add a sanity check for catalog btree node size Edward Adam Davis
@ 2026-04-15 22:32 ` Viacheslav Dubeyko
2026-04-16 4:09 ` Edward Adam Davis
0 siblings, 1 reply; 18+ messages in thread
From: Viacheslav Dubeyko @ 2026-04-15 22:32 UTC (permalink / raw)
To: Edward Adam Davis, syzbot+217eb327242d08197efb
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzkaller-bugs
On Wed, 2026-04-15 at 16:29 +0800, Edward Adam Davis wrote:
> Syzbot reported a uninit-value bug in [1], during the file system mounting
> process, specifically while loading the catalog, a corrupted node_size
> value of 1 caused the rec_off argument passed to hfs_bnode_read_u16()
> (within hfs_bnode_find()) to be excessively large. Consequently, the
> function failed to return a valid value to initialize the off variable,
> triggering the bug [1].
>
> To prevent similar issues, a check for the catalog btree node size has
> been added within the hfsplus_btree_open() function.
>
> [1]
> BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
> hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
> get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
> get_tree_bdev+0x38/0x50 fs/super.c:1717
> hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
> vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
> fc_mount fs/namespace.c:1193 [inline]
>
> Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
> Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> fs/hfsplus/btree.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
> index 761c74ccd653..61050ffe425e 100644
> --- a/fs/hfsplus/btree.c
> +++ b/fs/hfsplus/btree.c
> @@ -337,6 +337,11 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
> pr_err("invalid catalog btree flag\n");
> goto fail_page;
> }
> + if (tree->node_size < 2) {
Every node starts from BTree node descriptor: struct hfs_bnode_desc. So, the
size of node cannot be lesser than that. However, technical specification
declares that: "The node size (which is expressed in bytes) must be power of
two, from 512 through 32,768, inclusive.". So, we can add more smart check here.
And, maybe, it makes sense to check the node size value at the places of using
it. What do you think?
But we have this check of node_size in hfs_btree_open() [1]:
size = tree->node_size;
if (!is_power_of_2(size))
goto fail_page;
If node size is 1, for example, then this check should fail to execute the
hfs_btree_open(). How, finally, do we have node_size == 1 during the
hfs_bnode_find()? I don't quite follow.
Thanks,
Slava.
> + pr_err("invalid catalog btree node size %u\n",
> + tree->node_size);
> + goto fail_page;
> + }
>
> if (test_bit(HFSPLUS_SB_HFSX, &HFSPLUS_SB(sb)->flags) &&
> (head->key_type == HFSPLUS_KEY_BINARY))
[1] https://elixir.bootlin.com/linux/v7.0/source/fs/hfsplus/btree.c#L232
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH] hfsplus: Add a sanity check for catalog btree node size
2026-04-15 22:32 ` Viacheslav Dubeyko
@ 2026-04-16 4:09 ` Edward Adam Davis
2026-04-16 9:53 ` [PATCH v2] hfsplus: Add a sanity check for " Edward Adam Davis
0 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-16 4:09 UTC (permalink / raw)
To: vdubeyko
Cc: eadavis, frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs
On Wed, 15 Apr 2026 15:32:59 -0700, Viacheslav Dubeyko wrote:
> > Syzbot reported a uninit-value bug in [1], during the file system mounting
> > process, specifically while loading the catalog, a corrupted node_size
> > value of 1 caused the rec_off argument passed to hfs_bnode_read_u16()
> > (within hfs_bnode_find()) to be excessively large. Consequently, the
> > function failed to return a valid value to initialize the off variable,
> > triggering the bug [1].
> >
> > To prevent similar issues, a check for the catalog btree node size has
> > been added within the hfsplus_btree_open() function.
> >
> > [1]
> > BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> > hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> > hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
> > hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
> > get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
> > get_tree_bdev+0x38/0x50 fs/super.c:1717
> > hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
> > vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
> > fc_mount fs/namespace.c:1193 [inline]
> >
> > Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
> > Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
> > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> > ---
> > fs/hfsplus/btree.c | 5 +++++
> > 1 file changed, 5 insertions(+)
> >
> > diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
> > index 761c74ccd653..61050ffe425e 100644
> > --- a/fs/hfsplus/btree.c
> > +++ b/fs/hfsplus/btree.c
> > @@ -337,6 +337,11 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
> > pr_err("invalid catalog btree flag\n");
> > goto fail_page;
> > }
> > + if (tree->node_size < 2) {
>
> Every node starts from BTree node descriptor: struct hfs_bnode_desc. So, the
> size of node cannot be lesser than that. However, technical specification
> declares that: "The node size (which is expressed in bytes) must be power of
> two, from 512 through 32,768, inclusive.". So, we can add more smart check here.
Perhaps it could be adjusted as follows:
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 61050ffe425e..287cef5b5c56 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -370,6 +370,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
}
size = tree->node_size;
+ if (size < sb->s_blocksize || size > HFSPLUS_NODE_MXSZ)
+ goto fail_page;
if (!is_power_of_2(size))
goto fail_page;
if (!tree->node_count)
>
> And, maybe, it makes sense to check the node size value at the places of using
> it. What do you think?
>
> But we have this check of node_size in hfs_btree_open() [1]:
>
> size = tree->node_size;
> if (!is_power_of_2(size))
> goto fail_page;
>
> If node size is 1, for example, then this check should fail to execute the
> hfs_btree_open(). How, finally, do we have node_size == 1 during the
> hfs_bnode_find()? I don't quite follow.
You overlooked that 2 to the power of 0 is 1.
Edward
BR
^ permalink raw reply related [flat|nested] 18+ messages in thread* [PATCH v2] hfsplus: Add a sanity check for btree node size
2026-04-16 4:09 ` Edward Adam Davis
@ 2026-04-16 9:53 ` Edward Adam Davis
2026-04-16 22:16 ` Viacheslav Dubeyko
0 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-16 9:53 UTC (permalink / raw)
To: eadavis
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs, vdubeyko
Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
during the file system mounting process, specifically while loading the
catalog, a corrupted node_size value of 1 caused the rec_off argument
passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
large. Consequently, the function failed to return a valid value to
initialize the off variable, triggering the bug [1].
Every node starts from BTree node descriptor: struct hfs_bnode_desc.
So, the size of node cannot be lesser than that. However, technical
specification declares that: "The node size (which is expressed in bytes)
must be power of two, from 512 through 32,768, inclusive." Add a check
for btree node size base on technical specification.
[1]
BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
v1 -> v2: change check base on technical specification
fs/hfsplus/btree.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 761c74ccd653..857705c3fe0d 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -365,6 +365,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
}
size = tree->node_size;
+ if (size < sb->s_blocksize || size > HFSPLUS_NODE_MXSZ)
+ goto fail_page;
if (!is_power_of_2(size))
goto fail_page;
if (!tree->node_count)
--
2.43.0
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [PATCH v2] hfsplus: Add a sanity check for btree node size
2026-04-16 9:53 ` [PATCH v2] hfsplus: Add a sanity check for " Edward Adam Davis
@ 2026-04-16 22:16 ` Viacheslav Dubeyko
2026-04-16 23:38 ` Edward Adam Davis
0 siblings, 1 reply; 18+ messages in thread
From: Viacheslav Dubeyko @ 2026-04-16 22:16 UTC (permalink / raw)
To: Edward Adam Davis
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs
On Thu, 2026-04-16 at 17:53 +0800, Edward Adam Davis wrote:
> Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
> during the file system mounting process, specifically while loading the
> catalog, a corrupted node_size value of 1 caused the rec_off argument
> passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
> large. Consequently, the function failed to return a valid value to
> initialize the off variable, triggering the bug [1].
>
> Every node starts from BTree node descriptor: struct hfs_bnode_desc.
> So, the size of node cannot be lesser than that. However, technical
> specification declares that: "The node size (which is expressed in bytes)
> must be power of two, from 512 through 32,768, inclusive." Add a check
> for btree node size base on technical specification.
>
> [1]
> BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
> hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
> get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
> get_tree_bdev+0x38/0x50 fs/super.c:1717
> hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
> vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
> fc_mount fs/namespace.c:1193 [inline]
>
> Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
> Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> v1 -> v2: change check base on technical specification
>
> fs/hfsplus/btree.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
> index 761c74ccd653..857705c3fe0d 100644
> --- a/fs/hfsplus/btree.c
> +++ b/fs/hfsplus/btree.c
> @@ -365,6 +365,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
> }
>
> size = tree->node_size;
> + if (size < sb->s_blocksize || size > HFSPLUS_NODE_MXSZ)
Technically speaking, you are right that b-tree node size should be aligned on
logical block size. However, I am not sure that mkfs.hfsplus restricts the
creation of volume with b-tree's node size smaller than logical block size but
still in the required range of sizes.
Maybe, we need to declare the constant of HFSPLUS_NODE_MINSZ (512) and to check
this constant instead of logical block size. What do you think?
Thanks,
Slava.
> + goto fail_page;
> if (!is_power_of_2(size))
> goto fail_page;
> if (!tree->node_count)
^ permalink raw reply [flat|nested] 18+ messages in thread* Re: [PATCH v2] hfsplus: Add a sanity check for btree node size
2026-04-16 22:16 ` Viacheslav Dubeyko
@ 2026-04-16 23:38 ` Edward Adam Davis
2026-04-16 23:44 ` [PATCH v3] " Edward Adam Davis
0 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-16 23:38 UTC (permalink / raw)
To: vdubeyko
Cc: eadavis, frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs
On Thu, 16 Apr 2026 15:16:15 -0700, Viacheslav Dubeyko wrote:
> > Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
> > during the file system mounting process, specifically while loading the
> > catalog, a corrupted node_size value of 1 caused the rec_off argument
> > passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
> > large. Consequently, the function failed to return a valid value to
> > initialize the off variable, triggering the bug [1].
> >
> > Every node starts from BTree node descriptor: struct hfs_bnode_desc.
> > So, the size of node cannot be lesser than that. However, technical
> > specification declares that: "The node size (which is expressed in bytes)
> > must be power of two, from 512 through 32,768, inclusive." Add a check
> > for btree node size base on technical specification.
> >
> > [1]
> > BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> > hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> > hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
> > hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
> > get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
> > get_tree_bdev+0x38/0x50 fs/super.c:1717
> > hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
> > vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
> > fc_mount fs/namespace.c:1193 [inline]
> >
> > Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
> > Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
> > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> > ---
> > v1 -> v2: change check base on technical specification
> >
> > fs/hfsplus/btree.c | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
> > index 761c74ccd653..857705c3fe0d 100644
> > --- a/fs/hfsplus/btree.c
> > +++ b/fs/hfsplus/btree.c
> > @@ -365,6 +365,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
> > }
> >
> > size = tree->node_size;
> > + if (size < sb->s_blocksize || size > HFSPLUS_NODE_MXSZ)
>
> Technically speaking, you are right that b-tree node size should be aligned on
> logical block size. However, I am not sure that mkfs.hfsplus restricts the
> creation of volume with b-tree's node size smaller than logical block size but
> still in the required range of sizes.
>
> Maybe, we need to declare the constant of HFSPLUS_NODE_MINSZ (512) and to check
> this constant instead of logical block size. What do you think?
Hmm, that's much safer.
Edward
BR
^ permalink raw reply [flat|nested] 18+ messages in thread* [PATCH v3] hfsplus: Add a sanity check for btree node size
2026-04-16 23:38 ` Edward Adam Davis
@ 2026-04-16 23:44 ` Edward Adam Davis
2026-04-16 23:52 ` Viacheslav Dubeyko
0 siblings, 1 reply; 18+ messages in thread
From: Edward Adam Davis @ 2026-04-16 23:44 UTC (permalink / raw)
To: eadavis
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs, vdubeyko
Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
during the file system mounting process, specifically while loading the
catalog, a corrupted node_size value of 1 caused the rec_off argument
passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
large. Consequently, the function failed to return a valid value to
initialize the off variable, triggering the bug [1].
Every node starts from BTree node descriptor: struct hfs_bnode_desc.
So, the size of node cannot be lesser than that. However, technical
specification declares that: "The node size (which is expressed in bytes)
must be power of two, from 512 through 32,768, inclusive." Add a check
for btree node size base on technical specification.
[1]
BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
get_tree_bdev+0x38/0x50 fs/super.c:1717
hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
fc_mount fs/namespace.c:1193 [inline]
Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Signed-off-by: Edward Adam Davis <eadavis@qq.com>
---
v1 -> v2: change check base on technical specification
v2 -> v3: using const min size
fs/hfsplus/btree.c | 2 ++
include/linux/hfs_common.h | 1 +
2 files changed, 3 insertions(+)
diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
index 761c74ccd653..394542a47e60 100644
--- a/fs/hfsplus/btree.c
+++ b/fs/hfsplus/btree.c
@@ -365,6 +365,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
}
size = tree->node_size;
+ if (size < HFSPLUS_NODE_MINSZ || size > HFSPLUS_NODE_MXSZ)
+ goto fail_page;
if (!is_power_of_2(size))
goto fail_page;
if (!tree->node_count)
diff --git a/include/linux/hfs_common.h b/include/linux/hfs_common.h
index 07dfc39630ab..45fb4c9ff9f5 100644
--- a/include/linux/hfs_common.h
+++ b/include/linux/hfs_common.h
@@ -513,6 +513,7 @@ struct hfs_btree_header_rec {
/* HFS+ BTree misc info */
#define HFSPLUS_TREE_HEAD 0
#define HFSPLUS_NODE_MXSZ 32768
+#define HFSPLUS_NODE_MINSZ 512
#define HFSPLUS_ATTR_TREE_NODE_SIZE 8192
#define HFSPLUS_BTREE_HDR_NODE_RECS_COUNT 3
#define HFSPLUS_BTREE_HDR_MAP_REC_INDEX 2 /* Map (bitmap) record in Header node */
--
2.43.0
^ permalink raw reply related [flat|nested] 18+ messages in thread* Re: [PATCH v3] hfsplus: Add a sanity check for btree node size
2026-04-16 23:44 ` [PATCH v3] " Edward Adam Davis
@ 2026-04-16 23:52 ` Viacheslav Dubeyko
0 siblings, 0 replies; 18+ messages in thread
From: Viacheslav Dubeyko @ 2026-04-16 23:52 UTC (permalink / raw)
To: Edward Adam Davis
Cc: frank.li, glaubitz, linux-fsdevel, linux-kernel, slava,
syzbot+217eb327242d08197efb, syzkaller-bugs
On Fri, 2026-04-17 at 07:44 +0800, Edward Adam Davis wrote:
> Syzbot reported an uninit-value bug in [1] with a corrupted HFS+ image,
> during the file system mounting process, specifically while loading the
> catalog, a corrupted node_size value of 1 caused the rec_off argument
> passed to hfs_bnode_read_u16() (within hfs_bnode_find()) to be excessively
> large. Consequently, the function failed to return a valid value to
> initialize the off variable, triggering the bug [1].
>
> Every node starts from BTree node descriptor: struct hfs_bnode_desc.
> So, the size of node cannot be lesser than that. However, technical
> specification declares that: "The node size (which is expressed in bytes)
> must be power of two, from 512 through 32,768, inclusive." Add a check
> for btree node size base on technical specification.
>
> [1]
> BUG: KMSAN: uninit-value in hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_bnode_find+0x141c/0x1600 fs/hfsplus/bnode.c:584
> hfsplus_btree_open+0x169a/0x1e40 fs/hfsplus/btree.c:382
> hfsplus_fill_super+0x111f/0x2770 fs/hfsplus/super.c:553
> get_tree_bdev_flags+0x6e6/0x920 fs/super.c:1694
> get_tree_bdev+0x38/0x50 fs/super.c:1717
> hfsplus_get_tree+0x35/0x40 fs/hfsplus/super.c:709
> vfs_get_tree+0xb3/0x5d0 fs/super.c:1754
> fc_mount fs/namespace.c:1193 [inline]
>
> Fixes: 8ad2c6a36ac4 ("hfsplus: validate b-tree node 0 bitmap at mount time")
> Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> v1 -> v2: change check base on technical specification
> v2 -> v3: using const min size
>
> fs/hfsplus/btree.c | 2 ++
> include/linux/hfs_common.h | 1 +
> 2 files changed, 3 insertions(+)
>
> diff --git a/fs/hfsplus/btree.c b/fs/hfsplus/btree.c
> index 761c74ccd653..394542a47e60 100644
> --- a/fs/hfsplus/btree.c
> +++ b/fs/hfsplus/btree.c
> @@ -365,6 +365,8 @@ struct hfs_btree *hfs_btree_open(struct super_block *sb, u32 id)
> }
>
> size = tree->node_size;
> + if (size < HFSPLUS_NODE_MINSZ || size > HFSPLUS_NODE_MXSZ)
> + goto fail_page;
> if (!is_power_of_2(size))
> goto fail_page;
> if (!tree->node_count)
> diff --git a/include/linux/hfs_common.h b/include/linux/hfs_common.h
> index 07dfc39630ab..45fb4c9ff9f5 100644
> --- a/include/linux/hfs_common.h
> +++ b/include/linux/hfs_common.h
> @@ -513,6 +513,7 @@ struct hfs_btree_header_rec {
> /* HFS+ BTree misc info */
> #define HFSPLUS_TREE_HEAD 0
> #define HFSPLUS_NODE_MXSZ 32768
> +#define HFSPLUS_NODE_MINSZ 512
> #define HFSPLUS_ATTR_TREE_NODE_SIZE 8192
> #define HFSPLUS_BTREE_HDR_NODE_RECS_COUNT 3
> #define HFSPLUS_BTREE_HDR_MAP_REC_INDEX 2 /* Map (bitmap) record in Header node */
Looks good. Thanks a lot for the fix.
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Thanks,
Slava.
^ permalink raw reply [flat|nested] 18+ messages in thread
* Forwarded: [PATCH] hfsplus: initialize data in hfs_bnode_read_u16 and
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
2026-04-15 0:52 ` Edward Adam Davis
2026-04-15 8:29 ` [PATCH] hfsplus: Add a sanity check for catalog btree node size Edward Adam Davis
@ 2026-04-17 10:12 ` syzbot
2026-04-17 16:21 ` Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read_u16 syzbot
` (4 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-04-17 10:12 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: [PATCH] hfsplus: initialize data in hfs_bnode_read_u16 and
Author: tristmd@gmail.com
From: Tristan Madani <tristan@talencesecurity.com>
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
hfs_bnode_read_u8
hfs_bnode_read_u16() and hfs_bnode_read_u8() declare a local variable
on the stack and pass it to hfs_bnode_read() to be filled. However,
when the requested offset is invalid (e.g. from a corrupted filesystem
image), hfs_bnode_read() returns early via the is_bnode_offset_valid()
check without writing to the buffer, leaving the local variable
uninitialized.
The callers then use the uninitialized value via be16_to_cpu() or
directly, which KMSAN flags as a use of uninitialized memory.
This is triggered during hfsplus_bnode_find() when mounting a crafted
HFS+ image with node_size=1 and invalid offsets.
Fix this by zero-initializing the local variables so that an invalid
read returns 0 rather than stack garbage.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfsplus/bnode.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index XXXXXXX..XXXXXXX 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -98,14 +98,14 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, int off, int len)
u16 hfs_bnode_read_u16(struct hfs_bnode *node, int off)
{
- __be16 data;
+ __be16 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 2);
return be16_to_cpu(data);
}
u8 hfs_bnode_read_u8(struct hfs_bnode *node, int off)
{
- u8 data;
+ u8 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 1);
return data;
--
2.43.0
^ permalink raw reply [flat|nested] 18+ messages in thread* Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read_u16
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (2 preceding siblings ...)
2026-04-17 10:12 ` Forwarded: [PATCH] hfsplus: initialize data in hfs_bnode_read_u16 and syzbot
@ 2026-04-17 16:21 ` syzbot
2026-04-18 13:39 ` Forwarded: Re: [syzbot] [hfs?] " syzbot
` (3 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-04-17 16:21 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read_u16
Author: tristmd@gmail.com
#syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>From 22a2a76dffd13b9a5bf3e41e13382714f3ffb459 Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Fri, 17 Apr 2026 16:15:17 +0000
Subject: [PATCH] hfsplus: initialize data in hfs_bnode_read_u16 and
hfs_bnode_read_u8
hfs_bnode_read_u16() and hfs_bnode_read_u8() declare local data
variables without initialization. If hfs_bnode_read() fails to
fully populate them (e.g., due to a corrupted node), the stale
stack values are returned, triggering KMSAN uninit-value.
Zero-initialize both variables.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfsplus/bnode.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index f8b5a8a..3579008 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -55,7 +55,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
{
- __be16 data;
+ __be16 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 2);
return be16_to_cpu(data);
@@ -63,7 +63,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
u8 hfs_bnode_read_u8(struct hfs_bnode *node, u32 off)
{
- u8 data;
+ u8 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 1);
return data;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Forwarded: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfs_bnode_read_u16
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (3 preceding siblings ...)
2026-04-17 16:21 ` Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read_u16 syzbot
@ 2026-04-18 13:39 ` syzbot
2026-04-30 22:42 ` Forwarded: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (2 subsequent siblings)
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-04-18 13:39 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfs_bnode_read_u16
Author: tristmd@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>From fa9693d02a6d2e2fda72504085400c761d5eec1f Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Sat, 18 Apr 2026 13:39:03 +0000
Subject: [PATCH] hfsplus: zero-initialize buffer in hfs_bnode_read
hfs_bnode_read() can return early without initializing the output
buffer when the offset is invalid or the requested length is
corrected to zero by check_and_correct_requested_length(). Callers
such as hfs_bnode_read_u16() pass stack-allocated buffers and use the
result unconditionally, leading to KMSAN uninit-value reports.
Rather than initializing at each individual call site, zero the buffer
at the start of hfs_bnode_read() before any validation checks. This
ensures the buffer is always in a known state regardless of which
early-return path is taken.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Tested-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfsplus/bnode.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index f8b5a8ae58ff5..14d1af2c7ba93 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -25,6 +25,8 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
struct page **pagep;
u32 l;
+ memset(buf, 0, len);
+
if (!is_bnode_offset_valid(node, off))
return;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Forwarded: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (4 preceding siblings ...)
2026-04-18 13:39 ` Forwarded: Re: [syzbot] [hfs?] " syzbot
@ 2026-04-30 22:42 ` syzbot
2026-05-01 0:00 ` Forwarded: #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master syzbot
2026-05-05 11:12 ` Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read syzbot
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-04-30 22:42 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find
Author: tristmd@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>From 481707e6b354ae2f36603d68c63364b56d6ee6b6 Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Thu, 30 Apr 2026 22:38:32 +0000
Subject: [PATCH 1/3] hfs/hfsplus: fix u32 overflow in
check_and_correct_requested_length
check_and_correct_requested_length() compares (off + len) against
node_size using u32 arithmetic. When the caller passes a large len
value (e.g. from an underflowed subtraction in hfs_brec_remove()),
off + len can wrap past 2^32 and produce a small result, causing the
bounds check to pass when it should fail.
For example, with off=14 and len=0xFFFFFFF2 (underflowed from
data_off - keyoffset - size in hfs_brec_remove), off + len wraps to 6,
which is less than a typical node_size of 512, so the check passes and
the subsequent memmove reads ~4GB past the node buffer.
Fix this by comparing len against (node_size - off) instead. Since
is_bnode_offset_valid() already guarantees off < node_size before this
point, the subtraction cannot underflow.
Reported-by: syzbot+6df204b70bf3261691c5@syzkaller.appspotmail.com
Reported-by: syzbot+e76bf3d19b85350571ac@syzkaller.appspotmail.com
Fixes: a431930c9bac ("hfs: fix slab-out-of-bounds in hfs_bnode_read()")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfs/bnode.c | 2 +-
fs/hfsplus/hfsplus_fs.h | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c
index 13d58c51fc46b..c00645a4a5733 100644
--- a/fs/hfs/bnode.c
+++ b/fs/hfs/bnode.c
@@ -41,7 +41,7 @@ u32 check_and_correct_requested_length(struct hfs_bnode *node, u32 off, u32 len)
node_size = node->tree->node_size;
- if ((off + len) > node_size) {
+ if (len > node_size - off) {
u32 new_len = node_size - off;
pr_err("requested length has been corrected: "
diff --git a/fs/hfsplus/hfsplus_fs.h b/fs/hfsplus/hfsplus_fs.h
index 3545b8dbf11c5..10b2dda3f8044 100644
--- a/fs/hfsplus/hfsplus_fs.h
+++ b/fs/hfsplus/hfsplus_fs.h
@@ -600,7 +600,7 @@ u32 check_and_correct_requested_length(struct hfs_bnode *node, u32 off, u32 len)
node_size = node->tree->node_size;
- if ((off + len) > node_size) {
+ if (len > node_size - off) {
u32 new_len = node_size - off;
pr_err("requested length has been corrected: "
--
2.47.3
>From 5eb857d2b6469a9857ce436345e8e18c5791c3ef Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Thu, 30 Apr 2026 22:39:00 +0000
Subject: [PATCH 2/3] hfs/hfsplus: initialize data buffer in hfs_bnode_read_u16
and hfs_bnode_read_u8
hfs_bnode_read_u16() and hfs_bnode_read_u8() declare local data buffers
without initialization, then pass them to hfs_bnode_read(). If
is_bnode_offset_valid() fails inside hfs_bnode_read(), the function
returns early without writing to the buffer, leaving it uninitialized.
The caller then returns the garbage value to its caller.
This triggers KMSAN uninit-value reports when a corrupted HFS+ image
has a node_size of 1, causing rec_off to underflow in hfs_bnode_find()
and the subsequent hfs_bnode_read_u16() to operate on an invalid offset.
Zero-initialize both buffers so that callers get a deterministic zero
value when the underlying read fails.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Fixes: a431930c9bac ("hfs: fix slab-out-of-bounds in hfs_bnode_read()")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfs/bnode.c | 4 ++--
fs/hfsplus/bnode.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c
index c00645a4a5733..08307faea7a68 100644
--- a/fs/hfs/bnode.c
+++ b/fs/hfs/bnode.c
@@ -97,7 +97,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
{
- __be16 data;
+ __be16 data = 0;
// optimize later...
hfs_bnode_read(node, &data, off, 2);
return be16_to_cpu(data);
@@ -105,7 +105,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
u8 hfs_bnode_read_u8(struct hfs_bnode *node, u32 off)
{
- u8 data;
+ u8 data = 0;
// optimize later...
hfs_bnode_read(node, &data, off, 1);
return data;
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index f8b5a8ae58ff5..35790085b5b2e 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -55,7 +55,7 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
{
- __be16 data;
+ __be16 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 2);
return be16_to_cpu(data);
@@ -63,7 +63,7 @@ u16 hfs_bnode_read_u16(struct hfs_bnode *node, u32 off)
u8 hfs_bnode_read_u8(struct hfs_bnode *node, u32 off)
{
- u8 data;
+ u8 data = 0;
/* TODO: optimize later... */
hfs_bnode_read(node, &data, off, 1);
return data;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Forwarded: #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (5 preceding siblings ...)
2026-04-30 22:42 ` Forwarded: Re: [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
@ 2026-05-01 0:00 ` syzbot
2026-05-05 11:12 ` Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read syzbot
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-05-01 0:00 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
Author: tristmd@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>From fa9693d02a6d2e2fda72504085400c761d5eec1f Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Sat, 18 Apr 2026 13:39:03 +0000
Subject: [PATCH] hfsplus: zero-initialize buffer in hfs_bnode_read
hfs_bnode_read() can return early without initializing the output
buffer when the offset is invalid or the requested length is
corrected to zero by check_and_correct_requested_length(). Callers
such as hfs_bnode_read_u16() pass stack-allocated buffers and use the
result unconditionally, leading to KMSAN uninit-value reports.
Rather than initializing at each individual call site, zero the buffer
at the start of hfs_bnode_read() before any validation checks. This
ensures the buffer is always in a known state regardless of which
early-return path is taken.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Tested-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfsplus/bnode.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index f8b5a8ae58ff5..14d1af2c7ba93 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -25,6 +25,8 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
struct page **pagep;
u32 l;
+ memset(buf, 0, len);
+
if (!is_bnode_offset_valid(node, off))
return;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread* Forwarded: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read
2026-04-14 23:20 [syzbot] [hfs?] KMSAN: uninit-value in hfsplus_bnode_find syzbot
` (6 preceding siblings ...)
2026-05-01 0:00 ` Forwarded: #syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master syzbot
@ 2026-05-05 11:12 ` syzbot
7 siblings, 0 replies; 18+ messages in thread
From: syzbot @ 2026-05-05 11:12 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] KMSAN: uninit-value in hfs_bnode_read
Author: tristmd@gmail.com
#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>From 9844dc36acf6c4c44348a5ea5ece3367423b0519 Mon Sep 17 00:00:00 2001
From: Tristan Madani <tristan@talencesecurity.com>
Date: Tue, 5 May 2026 11:08:43 +0000
Subject: [PATCH v2 2/2] hfs/hfsplus: zero-initialize buffer in hfs_bnode_read
hfs_bnode_read() can return early without writing to the output buffer
when is_bnode_offset_valid() fails or when check_and_correct_requested_
length() corrects the length to zero. Callers such as hfs_bnode_read_
u16() and hfs_bnode_read_u8() pass stack-allocated buffers and use the
result unconditionally, leading to KMSAN uninit-value reports.
Rather than initializing at each individual call site, zero the buffer
at the start of hfs_bnode_read() before any validation checks. This
ensures all callers in both hfs and hfsplus get a deterministic zero
value regardless of which early-return path is taken.
Reported-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=217eb327242d08197efb
Tested-by: syzbot+217eb327242d08197efb@syzkaller.appspotmail.com
Fixes: a431930c9bac ("hfs: fix slab-out-of-bounds in hfs_bnode_read()")
Cc: stable@vger.kernel.org
Signed-off-by: Tristan Madani <tristan@talencesecurity.com>
---
fs/hfs/bnode.c | 2 ++
fs/hfsplus/bnode.c | 2 ++
2 files changed, 4 insertions(+)
diff --git a/fs/hfs/bnode.c b/fs/hfs/bnode.c
index 9571f33b91085..25cef62fbba6d 100644
--- a/fs/hfs/bnode.c
+++ b/fs/hfs/bnode.c
@@ -64,6 +64,8 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
u32 bytes_read;
u32 bytes_to_read;
+ memset(buf, 0, len);
+
if (!is_bnode_offset_valid(node, off))
return;
diff --git a/fs/hfsplus/bnode.c b/fs/hfsplus/bnode.c
index f8b5a8ae58ff5..14d1af2c7ba93 100644
--- a/fs/hfsplus/bnode.c
+++ b/fs/hfsplus/bnode.c
@@ -25,6 +25,8 @@ void hfs_bnode_read(struct hfs_bnode *node, void *buf, u32 off, u32 len)
struct page **pagep;
u32 l;
+ memset(buf, 0, len);
+
if (!is_bnode_offset_valid(node, off))
return;
--
2.47.3
^ permalink raw reply related [flat|nested] 18+ messages in thread