Re: [syzbot] [integrity?] [lsm?] KMSAN: uninit-value in ima_add_template_entry

Re: [syzbot] [integrity?] [lsm?] KMSAN: uninit-value in ima_add_template_entry

[Tetsuo Handa]

On 2024/02/20 19:40, Roberto Sassu wrote:
> On Mon, 2024-02-19 at 22:41 -0800, syzbot wrote:
>> Hello,
>>
>> syzbot found the following issue on:
>>
>> HEAD commit:    4f5e5092fdbf Merge tag 'net-6.8-rc5' of git://git.kernel.o..
>> git tree:       upstream
>> console output: https://syzkaller.appspot.com/x/log.txt?x=135ba81c180000
>> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
>> dashboard link: https://syzkaller.appspot.com/bug?extid=7bc44a489f0ef0670bd5
>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

> I would add the VFS people in CC, in case they have some ideas.

This is an erofs bug. Since the filesystem image in the reproducer
is crafted, decompression generates bogus result and
z_erofs_transform_plain() misbehaves.

You can obtain a single-threaded reproducer from
https://syzkaller.appspot.com/x/repro.c?x=1256096a180000 with below diff.

----------------------------------------
--- old/1256096a180000.c
+++ new/1256096a180000.c
@@ -676,6 +676,6 @@
   syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
           /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
           /*offset=*/0ul);
-  loop();
+  execute_one();
   return 0;
 }
----------------------------------------

With CONFIG_EROFS_FS_DEBUG=y, the reproducer hits DBG_BUGON().
With debug printk() shown below, you can get output shown below.

----------------------------------------
diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index d4cee95af14c..f221133a0731 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -323,7 +323,11 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
 	u8 *kin;
 
-	DBG_BUGON(rq->outputsize > rq->inputsize);
+	if (rq->outputsize > rq->inputsize) {
+		pr_err("rq->inputsize=%u rq->outputsize=%u\n", rq->inputsize, rq->outputsize);
+		pr_err("rq->pageofs_in=%u rq->pageofs_out=%u\n", rq->pageofs_in, rq->pageofs_out);
+		pr_err("nrpages_in=%u nrpages_out=%u\n", nrpages_in, nrpages_out);
+	}
 	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
 		cur = bs - (rq->pageofs_out & (bs - 1));
 		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
@@ -352,7 +356,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 		do {
 			no = (rq->pageofs_out + cur + pi) >> PAGE_SHIFT;
 			po = (rq->pageofs_out + cur + pi) & ~PAGE_MASK;
-			DBG_BUGON(no >= nrpages_out);
+			if (no >= nrpages_out)
+				pr_err("no=%u nrpages_out=%u\n", no, nrpages_out);
 			cnt = min(insz - pi, PAGE_SIZE - po);
 			if (rq->out[no] == rq->in[ni]) {
 				memmove(kin + po,
@@ -366,7 +371,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 		} while (pi < insz);
 		kunmap_local(kin);
 	}
-	DBG_BUGON(ni > nrpages_in);
+	if (ni > nrpages_in)
+		pr_err("ni=%u nrpages_in=%u\n", ni, nrpages_in);
 	return 0;
 }
 
----------------------------------------

----------------------------------------
[  138.991810][ T2983] loop0: detected capacity change from 0 to 16
[  139.804002][ T2983] erofs: (device loop0): mounted with root inode @ nid 36.
[  139.810464][   T87] erofs: rq->inputsize=4096 rq->outputsize=8194
[  139.821540][   T87] erofs: rq->pageofs_in=0 rq->pageofs_out=0
[  139.824347][   T87] erofs: nrpages_in=1 nrpages_out=3
[  139.827008][   T87] erofs: ni=3 nrpages_in=1
[  139.873777][ T2983] =====================================================
[  139.881268][ T2983] BUG: KMSAN: uninit-value in ima_add_template_entry+0x626/0xa80
----------------------------------------

#syz set subsystems: erofs

Re: [syzbot] [integrity?] [lsm?] KMSAN: uninit-value in ima_add_template_entry

[Gao Xiang]

On 2024/3/3 22:54, Tetsuo Handa wrote:
> On 2024/02/20 19:40, Roberto Sassu wrote:
>> On Mon, 2024-02-19 at 22:41 -0800, syzbot wrote:
>>> Hello,
>>>
>>> syzbot found the following issue on:
>>>
>>> HEAD commit:    4f5e5092fdbf Merge tag 'net-6.8-rc5' of git://git.kernel.o..
>>> git tree:       upstream
>>> console output: https://syzkaller.appspot.com/x/log.txt?x=135ba81c180000
>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
>>> dashboard link: https://syzkaller.appspot.com/bug?extid=7bc44a489f0ef0670bd5
>>> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
>> I would add the VFS people in CC, in case they have some ideas.
> 
> This is an erofs bug. Since the filesystem image in the reproducer
> is crafted, decompression generates bogus result and
> z_erofs_transform_plain() misbehaves.

Yes, thanks for looking into this.  It seems it was introduced by
a new commit 1ca01520148a this cycle, let me find more clues and
make a fix for this.

Thanks,
Gao Xiang

> 
> You can obtain a single-threaded reproducer from
> https://syzkaller.appspot.com/x/repro.c?x=1256096a180000 with below diff.
> 
> ----------------------------------------
> --- old/1256096a180000.c
> +++ new/1256096a180000.c
> @@ -676,6 +676,6 @@
>     syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
>             /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
>             /*offset=*/0ul);
> -  loop();
> +  execute_one();
>     return 0;
>   }
> ----------------------------------------
> 
> With CONFIG_EROFS_FS_DEBUG=y, the reproducer hits DBG_BUGON().
> With debug printk() shown below, you can get output shown below.
> 
> ----------------------------------------
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index d4cee95af14c..f221133a0731 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -323,7 +323,11 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>   	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
>   	u8 *kin;
>   
> -	DBG_BUGON(rq->outputsize > rq->inputsize);
> +	if (rq->outputsize > rq->inputsize) {
> +		pr_err("rq->inputsize=%u rq->outputsize=%u\n", rq->inputsize, rq->outputsize);
> +		pr_err("rq->pageofs_in=%u rq->pageofs_out=%u\n", rq->pageofs_in, rq->pageofs_out);
> +		pr_err("nrpages_in=%u nrpages_out=%u\n", nrpages_in, nrpages_out);
> +	}
>   	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
>   		cur = bs - (rq->pageofs_out & (bs - 1));
>   		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
> @@ -352,7 +356,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>   		do {
>   			no = (rq->pageofs_out + cur + pi) >> PAGE_SHIFT;
>   			po = (rq->pageofs_out + cur + pi) & ~PAGE_MASK;
> -			DBG_BUGON(no >= nrpages_out);
> +			if (no >= nrpages_out)
> +				pr_err("no=%u nrpages_out=%u\n", no, nrpages_out);
>   			cnt = min(insz - pi, PAGE_SIZE - po);
>   			if (rq->out[no] == rq->in[ni]) {
>   				memmove(kin + po,
> @@ -366,7 +371,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>   		} while (pi < insz);
>   		kunmap_local(kin);
>   	}
> -	DBG_BUGON(ni > nrpages_in);
> +	if (ni > nrpages_in)
> +		pr_err("ni=%u nrpages_in=%u\n", ni, nrpages_in);
>   	return 0;
>   }
>   
> ----------------------------------------
> 
> ----------------------------------------
> [  138.991810][ T2983] loop0: detected capacity change from 0 to 16
> [  139.804002][ T2983] erofs: (device loop0): mounted with root inode @ nid 36.
> [  139.810464][   T87] erofs: rq->inputsize=4096 rq->outputsize=8194
> [  139.821540][   T87] erofs: rq->pageofs_in=0 rq->pageofs_out=0
> [  139.824347][   T87] erofs: nrpages_in=1 nrpages_out=3
> [  139.827008][   T87] erofs: ni=3 nrpages_in=1
> [  139.873777][ T2983] =====================================================
> [  139.881268][ T2983] BUG: KMSAN: uninit-value in ima_add_template_entry+0x626/0xa80
> ----------------------------------------
> 
> #syz set subsystems: erofs

[PATCH] erofs: fix uninitialized page cache reported by KMSAN

[Gao Xiang]

syzbot reports a KMSAN reproducer [1] which generates a crafted
filesystem image and causes IMA to read uninitialized page cache.

Later, (rq->outputsize > rq->inputsize) will be formally supported
after either large uncompressed pclusters (> block size) or big
lclusters are landed.  However, currently there is no way to generate
such filesystems by using mkfs.erofs.

Thus, let's mark this condition as unsupported for now.

[1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com

Reported-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com
Fixes: 1ca01520148a ("erofs: refine z_erofs_transform_plain() for sub-page block support")
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/decompressor.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
index d4cee95af14c..2ec9b2bb628d 100644
--- a/fs/erofs/decompressor.c
+++ b/fs/erofs/decompressor.c
@@ -323,7 +323,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
 	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
 	u8 *kin;
 
-	DBG_BUGON(rq->outputsize > rq->inputsize);
+	if (rq->outputsize > rq->inputsize)
+		return -EOPNOTSUPP;
 	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
 		cur = bs - (rq->pageofs_out & (bs - 1));
 		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
-- 
2.39.3

Re: [PATCH] erofs: fix uninitialized page cache reported by KMSAN

[Gao Xiang]

#syz test git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev-test

On 2024/3/4 11:53, Gao Xiang wrote:
> syzbot reports a KMSAN reproducer [1] which generates a crafted
> filesystem image and causes IMA to read uninitialized page cache.
> 
> Later, (rq->outputsize > rq->inputsize) will be formally supported
> after either large uncompressed pclusters (> block size) or big
> lclusters are landed.  However, currently there is no way to generate
> such filesystems by using mkfs.erofs.
> 
> Thus, let's mark this condition as unsupported for now.
> 
> [1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com
> 
> Reported-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com
> Fixes: 1ca01520148a ("erofs: refine z_erofs_transform_plain() for sub-page block support")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
>   fs/erofs/decompressor.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index d4cee95af14c..2ec9b2bb628d 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -323,7 +323,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>   	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
>   	u8 *kin;
>   
> -	DBG_BUGON(rq->outputsize > rq->inputsize);
> +	if (rq->outputsize > rq->inputsize)
> +		return -EOPNOTSUPP;
>   	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
>   		cur = bs - (rq->pageofs_out & (bs - 1));
>   		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;

Re: [syzbot] [erofs] KMSAN: uninit-value in ima_add_template_entry

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-and-tested-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com

Tested on:

commit:         4288d8d1 erofs: fix uninitialized page cache reported ..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git dev-test
console output: https://syzkaller.appspot.com/x/log.txt?x=10893754180000
kernel config:  https://syzkaller.appspot.com/x/.config?x=db27810a659d0b3d
dashboard link: https://syzkaller.appspot.com/bug?extid=7bc44a489f0ef0670bd5
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.
Note: testing is done by a robot and is best-effort only.

Re: [syzbot] [integrity?] [lsm?] KMSAN: uninit-value in ima_add_template_entry

[Roberto Sassu]

On Sun, 2024-03-03 at 23:54 +0900, Tetsuo Handa wrote:
> On 2024/02/20 19:40, Roberto Sassu wrote:
> > On Mon, 2024-02-19 at 22:41 -0800, syzbot wrote:
> > > Hello,
> > > 
> > > syzbot found the following issue on:
> > > 
> > > HEAD commit:    4f5e5092fdbf Merge tag 'net-6.8-rc5' of git://git.kernel.o..
> > > git tree:       upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=135ba81c180000
> > > kernel config:  https://syzkaller.appspot.com/x/.config?x=e3dd779fba027968
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=7bc44a489f0ef0670bd5
> > > compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> 
> > I would add the VFS people in CC, in case they have some ideas.
> 
> This is an erofs bug. Since the filesystem image in the reproducer
> is crafted, decompression generates bogus result and
> z_erofs_transform_plain() misbehaves.

Thank you Tetsuo, and Gao Xiang for fixing it!

Roberto

> You can obtain a single-threaded reproducer from
> https://syzkaller.appspot.com/x/repro.c?x=1256096a180000 with below diff.
> 
> ----------------------------------------
> --- old/1256096a180000.c
> +++ new/1256096a180000.c
> @@ -676,6 +676,6 @@
>    syscall(__NR_mmap, /*addr=*/0x21000000ul, /*len=*/0x1000ul, /*prot=*/0ul,
>            /*flags=MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE*/ 0x32ul, /*fd=*/-1,
>            /*offset=*/0ul);
> -  loop();
> +  execute_one();
>    return 0;
>  }
> ----------------------------------------
> 
> With CONFIG_EROFS_FS_DEBUG=y, the reproducer hits DBG_BUGON().
> With debug printk() shown below, you can get output shown below.
> 
> ----------------------------------------
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index d4cee95af14c..f221133a0731 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -323,7 +323,11 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
>  	u8 *kin;
>  
> -	DBG_BUGON(rq->outputsize > rq->inputsize);
> +	if (rq->outputsize > rq->inputsize) {
> +		pr_err("rq->inputsize=%u rq->outputsize=%u\n", rq->inputsize, rq->outputsize);
> +		pr_err("rq->pageofs_in=%u rq->pageofs_out=%u\n", rq->pageofs_in, rq->pageofs_out);
> +		pr_err("nrpages_in=%u nrpages_out=%u\n", nrpages_in, nrpages_out);
> +	}
>  	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
>  		cur = bs - (rq->pageofs_out & (bs - 1));
>  		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
> @@ -352,7 +356,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  		do {
>  			no = (rq->pageofs_out + cur + pi) >> PAGE_SHIFT;
>  			po = (rq->pageofs_out + cur + pi) & ~PAGE_MASK;
> -			DBG_BUGON(no >= nrpages_out);
> +			if (no >= nrpages_out)
> +				pr_err("no=%u nrpages_out=%u\n", no, nrpages_out);
>  			cnt = min(insz - pi, PAGE_SIZE - po);
>  			if (rq->out[no] == rq->in[ni]) {
>  				memmove(kin + po,
> @@ -366,7 +371,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  		} while (pi < insz);
>  		kunmap_local(kin);
>  	}
> -	DBG_BUGON(ni > nrpages_in);
> +	if (ni > nrpages_in)
> +		pr_err("ni=%u nrpages_in=%u\n", ni, nrpages_in);
>  	return 0;
>  }
>  
> ----------------------------------------
> 
> ----------------------------------------
> [  138.991810][ T2983] loop0: detected capacity change from 0 to 16
> [  139.804002][ T2983] erofs: (device loop0): mounted with root inode @ nid 36.
> [  139.810464][   T87] erofs: rq->inputsize=4096 rq->outputsize=8194
> [  139.821540][   T87] erofs: rq->pageofs_in=0 rq->pageofs_out=0
> [  139.824347][   T87] erofs: nrpages_in=1 nrpages_out=3
> [  139.827008][   T87] erofs: ni=3 nrpages_in=1
> [  139.873777][ T2983] =====================================================
> [  139.881268][ T2983] BUG: KMSAN: uninit-value in ima_add_template_entry+0x626/0xa80
> ----------------------------------------
> 
> #syz set subsystems: erofs

Re: [PATCH] erofs: fix uninitialized page cache reported by KMSAN

[Sandeep Dhavale via Linux-erofs]

On Sun, Mar 3, 2024 at 7:54 PM Gao Xiang <hsiangkao@linux.alibaba.com> wrote:
>
> syzbot reports a KMSAN reproducer [1] which generates a crafted
> filesystem image and causes IMA to read uninitialized page cache.
>
> Later, (rq->outputsize > rq->inputsize) will be formally supported
> after either large uncompressed pclusters (> block size) or big
> lclusters are landed.  However, currently there is no way to generate
> such filesystems by using mkfs.erofs.
>
> Thus, let's mark this condition as unsupported for now.
>
> [1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com
>
> Reported-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com
> Fixes: 1ca01520148a ("erofs: refine z_erofs_transform_plain() for sub-page block support")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
>  fs/erofs/decompressor.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index d4cee95af14c..2ec9b2bb628d 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -323,7 +323,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>         unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
>         u8 *kin;
>
> -       DBG_BUGON(rq->outputsize > rq->inputsize);
> +       if (rq->outputsize > rq->inputsize)
> +               return -EOPNOTSUPP;
>         if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
>                 cur = bs - (rq->pageofs_out & (bs - 1));
>                 pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;
> --
> 2.39.3
>
LGTM.
Reviewed-by: Sandeep Dhavale <dhavale@google.com>

Thanks,
Sandeep.

Re: [PATCH] erofs: fix uninitialized page cache reported by KMSAN

[Yue Hu]

On Mon,  4 Mar 2024 11:53:39 +0800
Gao Xiang <hsiangkao@linux.alibaba.com> wrote:

> syzbot reports a KMSAN reproducer [1] which generates a crafted
> filesystem image and causes IMA to read uninitialized page cache.
> 
> Later, (rq->outputsize > rq->inputsize) will be formally supported
> after either large uncompressed pclusters (> block size) or big
> lclusters are landed.  However, currently there is no way to generate
> such filesystems by using mkfs.erofs.
> 
> Thus, let's mark this condition as unsupported for now.
> 
> [1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com
> 
> Reported-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com
> Fixes: 1ca01520148a ("erofs: refine z_erofs_transform_plain() for sub-page block support")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> ---
>  fs/erofs/decompressor.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/erofs/decompressor.c b/fs/erofs/decompressor.c
> index d4cee95af14c..2ec9b2bb628d 100644
> --- a/fs/erofs/decompressor.c
> +++ b/fs/erofs/decompressor.c
> @@ -323,7 +323,8 @@ static int z_erofs_transform_plain(struct z_erofs_decompress_req *rq,
>  	unsigned int cur = 0, ni = 0, no, pi, po, insz, cnt;
>  	u8 *kin;
>  
> -	DBG_BUGON(rq->outputsize > rq->inputsize);
> +	if (rq->outputsize > rq->inputsize)
> +		return -EOPNOTSUPP;
>  	if (rq->alg == Z_EROFS_COMPRESSION_INTERLACED) {
>  		cur = bs - (rq->pageofs_out & (bs - 1));
>  		pi = (rq->pageofs_in + rq->inputsize - cur) & ~PAGE_MASK;

Reviewed-by: Yue Hu <huyue2@coolpad.com>

Re: [PATCH] erofs: fix uninitialized page cache reported by KMSAN

[Chao Yu]

On 2024/3/4 11:53, Gao Xiang wrote:
> syzbot reports a KMSAN reproducer [1] which generates a crafted
> filesystem image and causes IMA to read uninitialized page cache.
> 
> Later, (rq->outputsize > rq->inputsize) will be formally supported
> after either large uncompressed pclusters (> block size) or big
> lclusters are landed.  However, currently there is no way to generate
> such filesystems by using mkfs.erofs.
> 
> Thus, let's mark this condition as unsupported for now.
> 
> [1] https://lore.kernel.org/r/0000000000002be12a0611ca7ff8@google.com
> 
> Reported-by: syzbot+7bc44a489f0ef0670bd5@syzkaller.appspotmail.com
> Fixes: 1ca01520148a ("erofs: refine z_erofs_transform_plain() for sub-page block support")
> Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,