* [PATCH] ovl: keep err zero after successful ovl_cache_get()
@ 2026-05-14 11:13 Nirmoy Das
2026-05-14 12:36 ` Amir Goldstein
2026-05-14 14:42 ` [PATCH v2] " Nirmoy Das
0 siblings, 2 replies; 8+ messages in thread
From: Nirmoy Das @ 2026-05-14 11:13 UTC (permalink / raw)
To: Miklos Szeredi, Amir Goldstein
Cc: Christian Brauner, linux-unionfs, linux-kernel, Nirmoy Das,
syzbot+a16fb0cce329a320661c, stable
ovl_iterate_merged() stores PTR_ERR(cache) in err before checking
IS_ERR(cache). On success err holds the truncated cache pointer and
can be returned as a bogus non-zero error.
The syzbot reproducer reaches this through overlay-on-overlay readdir:
getdents64
iterate_dir(outer overlay file)
ovl_iterate_merged()
ovl_cache_get()
ovl_dir_read_merged()
ovl_dir_read()
iterate_dir(inner overlay file)
ovl_iterate_merged()
Only compute PTR_ERR(cache) on the error path.
Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard")
Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c
Cc: stable@vger.kernel.org
Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com>
---
fs/overlayfs/readdir.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c
index 1dcc75b3a90f9..0d471064cfea1 100644
--- a/fs/overlayfs/readdir.c
+++ b/fs/overlayfs/readdir.c
@@ -844,9 +844,8 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx)
struct ovl_dir_cache *cache;
cache = ovl_cache_get(dentry);
- err = PTR_ERR(cache);
if (IS_ERR(cache))
- return err;
+ return PTR_ERR(cache);
od->cache = cache;
ovl_seek_cursor(od, ctx->pos);
--
2.43.0
^ permalink raw reply related [flat|nested] 8+ messages in thread* Re: [PATCH] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 11:13 [PATCH] ovl: keep err zero after successful ovl_cache_get() Nirmoy Das @ 2026-05-14 12:36 ` Amir Goldstein 2026-05-14 14:37 ` Nirmoy Das 2026-05-14 14:42 ` [PATCH v2] " Nirmoy Das 1 sibling, 1 reply; 8+ messages in thread From: Amir Goldstein @ 2026-05-14 12:36 UTC (permalink / raw) To: Nirmoy Das Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable Hi Nirmoy! Nice catch! On Thu, May 14, 2026 at 1:14 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: > > ovl_iterate_merged() stores PTR_ERR(cache) in err before checking > IS_ERR(cache). On success err holds the truncated cache pointer and > can be returned as a bogus non-zero error. > > The syzbot reproducer reaches this through overlay-on-overlay readdir: > > getdents64 > iterate_dir(outer overlay file) > ovl_iterate_merged() > ovl_cache_get() > ovl_dir_read_merged() > ovl_dir_read() > iterate_dir(inner overlay file) > ovl_iterate_merged() > > Only compute PTR_ERR(cache) on the error path. > > Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") > Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c Does this fix really close the bug? The report is a UAF, which was fixed by the other patch. Right? > Cc: stable@vger.kernel.org > Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> > --- > fs/overlayfs/readdir.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c > index 1dcc75b3a90f9..0d471064cfea1 100644 > --- a/fs/overlayfs/readdir.c > +++ b/fs/overlayfs/readdir.c > @@ -844,9 +844,8 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) > struct ovl_dir_cache *cache; > > cache = ovl_cache_get(dentry); > - err = PTR_ERR(cache); > if (IS_ERR(cache)) > - return err; > + return PTR_ERR(cache); > This is good but also no point for returning err at end on function at all: --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -838,7 +838,7 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) struct ovl_dir_file *od = file->private_data; struct dentry *dentry = file->f_path.dentry; struct ovl_cache_entry *p; - int err = 0; + int err; if (!od->cache) { struct ovl_dir_cache *cache; @@ -869,7 +869,7 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) od->cursor = p->l_node.next; ctx->pos++; } - return err; + return 0; } Thanks, Amir. ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 12:36 ` Amir Goldstein @ 2026-05-14 14:37 ` Nirmoy Das 0 siblings, 0 replies; 8+ messages in thread From: Nirmoy Das @ 2026-05-14 14:37 UTC (permalink / raw) To: Amir Goldstein Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable Hi Amir, On 14.05.26 15:36, Amir Goldstein wrote: > Hi Nirmoy! > > Nice catch! > > On Thu, May 14, 2026 at 1:14 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: >> ovl_iterate_merged() stores PTR_ERR(cache) in err before checking >> IS_ERR(cache). On success err holds the truncated cache pointer and >> can be returned as a bogus non-zero error. >> >> The syzbot reproducer reaches this through overlay-on-overlay readdir: >> >> getdents64 >> iterate_dir(outer overlay file) >> ovl_iterate_merged() >> ovl_cache_get() >> ovl_dir_read_merged() >> ovl_dir_read() >> iterate_dir(inner overlay file) >> ovl_iterate_merged() >> >> Only compute PTR_ERR(cache) on the error path. >> >> Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") >> Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com >> Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c > Does this fix really close the bug? > The report is a UAF, which was fixed by the other patch. > Right? I think the previous patch was masking this. KASAN says "maybe wild-memory-access in range". If I'm not wrong, we would see "use-after-free" or "slab-use-after-free" for a real UAF. Reproducing on aarch64 virtme-ng + KASAN with the unpatched kernel I get: Unable to handle kernel paging request at virtual address ffffffffc1c02d50 KASAN: maybe wild-memory-access in range [0x0003fffe0e016a80-0x0003fffe0e016a87] [ffffffffc1c02d50] pgd=0..., p4d=..., pud=..., pmd=0000000000000000 The patch fixes the issue. Without the fix the reproducer hits the crashes around ~1500 iteration. With the fix applied it runs > 5000 iterations with no error. > >> Cc: stable@vger.kernel.org >> Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> >> --- >> fs/overlayfs/readdir.c | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c >> index 1dcc75b3a90f9..0d471064cfea1 100644 >> --- a/fs/overlayfs/readdir.c >> +++ b/fs/overlayfs/readdir.c >> @@ -844,9 +844,8 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) >> struct ovl_dir_cache *cache; >> >> cache = ovl_cache_get(dentry); >> - err = PTR_ERR(cache); >> if (IS_ERR(cache)) >> - return err; >> + return PTR_ERR(cache); >> > This is good but also no point for returning err at end on function at all: > > --- a/fs/overlayfs/readdir.c > +++ b/fs/overlayfs/readdir.c > @@ -838,7 +838,7 @@ static int ovl_iterate_merged(struct file *file, > struct dir_context *ctx) > struct ovl_dir_file *od = file->private_data; > struct dentry *dentry = file->f_path.dentry; > struct ovl_cache_entry *p; > - int err = 0; > + int err; > > if (!od->cache) { > struct ovl_dir_cache *cache; > @@ -869,7 +869,7 @@ static int ovl_iterate_merged(struct file *file, > struct dir_context *ctx) > od->cursor = p->l_node.next; > ctx->pos++; > } > - return err; > + return 0; > } I will send a v2 with this suggestion. Regards, Nirmoy > Thanks, > Amir. ^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH v2] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 11:13 [PATCH] ovl: keep err zero after successful ovl_cache_get() Nirmoy Das 2026-05-14 12:36 ` Amir Goldstein @ 2026-05-14 14:42 ` Nirmoy Das 2026-05-14 15:26 ` Amir Goldstein 1 sibling, 1 reply; 8+ messages in thread From: Nirmoy Das @ 2026-05-14 14:42 UTC (permalink / raw) To: Miklos Szeredi, Amir Goldstein Cc: Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable, Nirmoy Das ovl_iterate_merged() stores PTR_ERR(cache) in err before checking IS_ERR(cache). On success err holds the truncated cache pointer and can be returned as a bogus non-zero error. The syzbot reproducer reaches this through overlay-on-overlay readdir: getdents64 iterate_dir(outer overlay file) ovl_iterate_merged() ovl_cache_get() ovl_dir_read_merged() ovl_dir_read() iterate_dir(inner overlay file) ovl_iterate_merged() Only compute PTR_ERR(cache) on the error path. Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c Cc: stable@vger.kernel.org Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> --- v2: - Drop the now-redundant 'int err = 0' initializer and the trailing 'return err' in ovl_iterate_merged(); err is only used inside the loop's update-check, so the function can just return 0 on success. (Amir Goldstein) - Link to v1: https://lore.kernel.org/all/20260514111354.3552538-1-nirmoyd@nvidia.com/ fs/overlayfs/readdir.c | 7 +++---- 1 file changed, 3 insertions(+), 4 deletions(-) diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c index 1dcc75b3a90f9..e7fe29cb6028b 100644 --- a/fs/overlayfs/readdir.c +++ b/fs/overlayfs/readdir.c @@ -838,15 +838,14 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) struct ovl_dir_file *od = file->private_data; struct dentry *dentry = file->f_path.dentry; struct ovl_cache_entry *p; - int err = 0; + int err; if (!od->cache) { struct ovl_dir_cache *cache; cache = ovl_cache_get(dentry); - err = PTR_ERR(cache); if (IS_ERR(cache)) - return err; + return PTR_ERR(cache); od->cache = cache; ovl_seek_cursor(od, ctx->pos); @@ -869,7 +868,7 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) od->cursor = p->l_node.next; ctx->pos++; } - return err; + return 0; } static bool ovl_need_adjust_d_ino(struct file *file) -- 2.43.0 ^ permalink raw reply related [flat|nested] 8+ messages in thread
* Re: [PATCH v2] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 14:42 ` [PATCH v2] " Nirmoy Das @ 2026-05-14 15:26 ` Amir Goldstein 2026-05-14 19:19 ` Amir Goldstein 0 siblings, 1 reply; 8+ messages in thread From: Amir Goldstein @ 2026-05-14 15:26 UTC (permalink / raw) To: Nirmoy Das Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable On Thu, May 14, 2026 at 4:43 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: > > ovl_iterate_merged() stores PTR_ERR(cache) in err before checking > IS_ERR(cache). On success err holds the truncated cache pointer and > can be returned as a bogus non-zero error. > > The syzbot reproducer reaches this through overlay-on-overlay readdir: > > getdents64 > iterate_dir(outer overlay file) > ovl_iterate_merged() > ovl_cache_get() > ovl_dir_read_merged() > ovl_dir_read() > iterate_dir(inner overlay file) > ovl_iterate_merged() > > Only compute PTR_ERR(cache) on the error path. > > Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") > Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c > Cc: stable@vger.kernel.org > Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> > --- > v2: > - Drop the now-redundant 'int err = 0' initializer and the trailing > 'return err' in ovl_iterate_merged(); err is only used inside the > loop's update-check, so the function can just return 0 on success. > (Amir Goldstein) > - Link to v1: > https://lore.kernel.org/all/20260514111354.3552538-1-nirmoyd@nvidia.com/ > I queue this up and will work on fortifying patches. Thanks for the thorough investigation and for nailing this! Amir. > fs/overlayfs/readdir.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) > > diff --git a/fs/overlayfs/readdir.c b/fs/overlayfs/readdir.c > index 1dcc75b3a90f9..e7fe29cb6028b 100644 > --- a/fs/overlayfs/readdir.c > +++ b/fs/overlayfs/readdir.c > @@ -838,15 +838,14 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) > struct ovl_dir_file *od = file->private_data; > struct dentry *dentry = file->f_path.dentry; > struct ovl_cache_entry *p; > - int err = 0; > + int err; > > if (!od->cache) { > struct ovl_dir_cache *cache; > > cache = ovl_cache_get(dentry); > - err = PTR_ERR(cache); > if (IS_ERR(cache)) > - return err; > + return PTR_ERR(cache); > > od->cache = cache; > ovl_seek_cursor(od, ctx->pos); > @@ -869,7 +868,7 @@ static int ovl_iterate_merged(struct file *file, struct dir_context *ctx) > od->cursor = p->l_node.next; > ctx->pos++; > } > - return err; > + return 0; > } > > static bool ovl_need_adjust_d_ino(struct file *file) > -- > 2.43.0 > ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 15:26 ` Amir Goldstein @ 2026-05-14 19:19 ` Amir Goldstein 2026-05-15 11:15 ` Nirmoy Das 0 siblings, 1 reply; 8+ messages in thread From: Amir Goldstein @ 2026-05-14 19:19 UTC (permalink / raw) To: Nirmoy Das Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable On Thu, May 14, 2026 at 5:26 PM Amir Goldstein <amir73il@gmail.com> wrote: > > On Thu, May 14, 2026 at 4:43 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: > > > > ovl_iterate_merged() stores PTR_ERR(cache) in err before checking > > IS_ERR(cache). On success err holds the truncated cache pointer and > > can be returned as a bogus non-zero error. > > > > The syzbot reproducer reaches this through overlay-on-overlay readdir: > > > > getdents64 > > iterate_dir(outer overlay file) > > ovl_iterate_merged() > > ovl_cache_get() > > ovl_dir_read_merged() > > ovl_dir_read() > > iterate_dir(inner overlay file) > > ovl_iterate_merged() > > > > Only compute PTR_ERR(cache) on the error path. > > > > Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") > > Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com > > Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c > > Cc: stable@vger.kernel.org > > Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> > > --- > > v2: > > - Drop the now-redundant 'int err = 0' initializer and the trailing > > 'return err' in ovl_iterate_merged(); err is only used inside the > > loop's update-check, so the function can just return 0 on success. > > (Amir Goldstein) > > - Link to v1: > > https://lore.kernel.org/all/20260514111354.3552538-1-nirmoyd@nvidia.com/ > > > > I queue this up and will work on fortifying patches. Nirmoy, I pushed fortify patches to ovl-fixes on my github [1]. Can you verify that the assertions trigger if you revert your fix and run the reproducer? I imagine they would trigger much more frequently than the KASAN warnings do. Thanks, Amir. [1] https://github.com/amir73il/linux/commits/ovl-fixes/ ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] ovl: keep err zero after successful ovl_cache_get() 2026-05-14 19:19 ` Amir Goldstein @ 2026-05-15 11:15 ` Nirmoy Das 2026-05-15 16:39 ` Amir Goldstein 0 siblings, 1 reply; 8+ messages in thread From: Nirmoy Das @ 2026-05-15 11:15 UTC (permalink / raw) To: Amir Goldstein Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable Hi Amir, On 14.05.26 22:19, Amir Goldstein wrote: > On Thu, May 14, 2026 at 5:26 PM Amir Goldstein <amir73il@gmail.com> wrote: >> On Thu, May 14, 2026 at 4:43 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: >>> ovl_iterate_merged() stores PTR_ERR(cache) in err before checking >>> IS_ERR(cache). On success err holds the truncated cache pointer and >>> can be returned as a bogus non-zero error. >>> >>> The syzbot reproducer reaches this through overlay-on-overlay readdir: >>> >>> getdents64 >>> iterate_dir(outer overlay file) >>> ovl_iterate_merged() >>> ovl_cache_get() >>> ovl_dir_read_merged() >>> ovl_dir_read() >>> iterate_dir(inner overlay file) >>> ovl_iterate_merged() >>> >>> Only compute PTR_ERR(cache) on the error path. >>> >>> Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") >>> Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com >>> Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> >>> --- >>> v2: >>> - Drop the now-redundant 'int err = 0' initializer and the trailing >>> 'return err' in ovl_iterate_merged(); err is only used inside the >>> loop's update-check, so the function can just return 0 on success. >>> (Amir Goldstein) >>> - Link to v1: >>> https://lore.kernel.org/all/20260514111354.3552538-1-nirmoyd@nvidia.com/ >>> >> I queue this up and will work on fortifying patches. > Nirmoy, > > I pushed fortify patches to ovl-fixes on my github [1]. > > Can you verify that the assertions trigger if you revert your fix > and run the reproducer? > > I imagine they would trigger much more frequently than the KASAN > warnings do. Yes, the assertion triggers with your ovl-fixes branch after reverting my fix. 9541f25af774 Revert "ovl: keep err zero after successful ovl_cache_get()" 1c067d912e47 ovl: add assertions in dir cache code 98e3a2d258e9 ovl: fix race between copy-up and open of a directory 4f80bb375112 ovl: keep err zero after successful ovl_cache_get() 18de6460b6bd ovl: opt-in for fortified ERR_PTR() 690bd87e1fef err_ptr.h: introduce ERR_PTR_SAFE() 7fd2df204f34 Linux 7.1-rc2 Running the syz reproducer with panic_on_warn=1 triggered: [ 55.404636] ------------[ cut here ]------------ [ 55.404646] WARNING: fs/overlayfs/readdir.c:511 at ovl_iterate+0x4c0/0x5bc, CPU#2: syz-ovl-iterate/14575 [ 55.406875] CPU: 2 UID: 0 PID: 14575 Comm: syz-ovl-iterate Not tainted 7.1.0-rc2-g9541f25af774 #1 PREEMPT [ 55.408328] pc : ovl_iterate+0x4c0/0x5bc [ 55.408632] lr : ovl_iterate+0x4b4/0x5bc [ 55.413504] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffffffffc152db40 [ 55.414036] Call trace: [ 55.414209] ovl_iterate+0x4c0/0x5bc (P) [ 55.414503] wrap_directory_iterator+0x60/0x90 [ 55.414809] shared_ovl_iterate+0x18/0x24 [ 55.415125] iterate_dir+0x10c/0x3a4 [ 55.415365] __arm64_sys_getdents64+0xe0/0x1e4 [ 55.417312] Kernel panic - not syncing: kernel: panic_on_warn set ... Regards, Nirmoy > > Thanks, > Amir. > > [1] https://github.com/amir73il/linux/commits/ovl-fixes/ ^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH v2] ovl: keep err zero after successful ovl_cache_get() 2026-05-15 11:15 ` Nirmoy Das @ 2026-05-15 16:39 ` Amir Goldstein 0 siblings, 0 replies; 8+ messages in thread From: Amir Goldstein @ 2026-05-15 16:39 UTC (permalink / raw) To: Nirmoy Das Cc: Miklos Szeredi, Christian Brauner, linux-unionfs, linux-kernel, syzbot+a16fb0cce329a320661c, stable On Fri, May 15, 2026 at 1:16 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: > > Hi Amir, > > On 14.05.26 22:19, Amir Goldstein wrote: > > On Thu, May 14, 2026 at 5:26 PM Amir Goldstein <amir73il@gmail.com> wrote: > >> On Thu, May 14, 2026 at 4:43 PM Nirmoy Das <nirmoyd@nvidia.com> wrote: > >>> ovl_iterate_merged() stores PTR_ERR(cache) in err before checking > >>> IS_ERR(cache). On success err holds the truncated cache pointer and > >>> can be returned as a bogus non-zero error. > >>> > >>> The syzbot reproducer reaches this through overlay-on-overlay readdir: > >>> > >>> getdents64 > >>> iterate_dir(outer overlay file) > >>> ovl_iterate_merged() > >>> ovl_cache_get() > >>> ovl_dir_read_merged() > >>> ovl_dir_read() > >>> iterate_dir(inner overlay file) > >>> ovl_iterate_merged() > >>> > >>> Only compute PTR_ERR(cache) on the error path. > >>> > >>> Fixes: d25e4b739f83 ("ovl: refactor ovl_iterate() and port to cred guard") > >>> Reported-by: syzbot+a16fb0cce329a320661c@syzkaller.appspotmail.com > >>> Closes: https://syzkaller.appspot.com/bug?extid=a16fb0cce329a320661c > >>> Cc: stable@vger.kernel.org > >>> Signed-off-by: Nirmoy Das <nirmoyd@nvidia.com> > >>> --- > >>> v2: > >>> - Drop the now-redundant 'int err = 0' initializer and the trailing > >>> 'return err' in ovl_iterate_merged(); err is only used inside the > >>> loop's update-check, so the function can just return 0 on success. > >>> (Amir Goldstein) > >>> - Link to v1: > >>> https://lore.kernel.org/all/20260514111354.3552538-1-nirmoyd@nvidia.com/ > >>> > >> I queue this up and will work on fortifying patches. > > Nirmoy, > > > > I pushed fortify patches to ovl-fixes on my github [1]. > > > > Can you verify that the assertions trigger if you revert your fix > > and run the reproducer? > > > > I imagine they would trigger much more frequently than the KASAN > > warnings do. > > > Yes, the assertion triggers with your ovl-fixes branch after reverting > my fix. > > 9541f25af774 Revert "ovl: keep err zero after successful ovl_cache_get()" > 1c067d912e47 ovl: add assertions in dir cache code > 98e3a2d258e9 ovl: fix race between copy-up and open of a directory > 4f80bb375112 ovl: keep err zero after successful ovl_cache_get() > 18de6460b6bd ovl: opt-in for fortified ERR_PTR() > 690bd87e1fef err_ptr.h: introduce ERR_PTR_SAFE() > 7fd2df204f34 Linux 7.1-rc2 > > Running the syz reproducer with panic_on_warn=1 triggered: > > [ 55.404636] ------------[ cut here ]------------ > [ 55.404646] WARNING: fs/overlayfs/readdir.c:511 at > ovl_iterate+0x4c0/0x5bc, CPU#2: syz-ovl-iterate/14575 > [ 55.406875] CPU: 2 UID: 0 PID: 14575 Comm: syz-ovl-iterate Not > tainted 7.1.0-rc2-g9541f25af774 #1 PREEMPT > [ 55.408328] pc : ovl_iterate+0x4c0/0x5bc > [ 55.408632] lr : ovl_iterate+0x4b4/0x5bc > [ 55.413504] x2 : 0000000000000000 x1 : 0000000000000000 x0 : > ffffffffc152db40 > [ 55.414036] Call trace: > [ 55.414209] ovl_iterate+0x4c0/0x5bc (P) > [ 55.414503] wrap_directory_iterator+0x60/0x90 > [ 55.414809] shared_ovl_iterate+0x18/0x24 > [ 55.415125] iterate_dir+0x10c/0x3a4 > [ 55.415365] __arm64_sys_getdents64+0xe0/0x1e4 > [ 55.417312] Kernel panic - not syncing: kernel: panic_on_warn set ... > Thanks for testing! Did it trigger faster than the KASAN warning? I'd imagine that it would? Thanks, Amir. ^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2026-05-15 16:39 UTC | newest] Thread overview: 8+ messages (download: mbox.gz follow: Atom feed -- links below jump to the message on this page -- 2026-05-14 11:13 [PATCH] ovl: keep err zero after successful ovl_cache_get() Nirmoy Das 2026-05-14 12:36 ` Amir Goldstein 2026-05-14 14:37 ` Nirmoy Das 2026-05-14 14:42 ` [PATCH v2] " Nirmoy Das 2026-05-14 15:26 ` Amir Goldstein 2026-05-14 19:19 ` Amir Goldstein 2026-05-15 11:15 ` Nirmoy Das 2026-05-15 16:39 ` Amir Goldstein
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