[syzbot] [overlayfs?] memory leak in ovl_parse_param

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 13d88ac54ddd Merge tag 'vfs-6.7.fsid' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=121cf047680000
kernel config: https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=15c7a6eb680000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=13f8b787680000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9bb27a01f17c/disk-13d88ac5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/fb496feed171/vmlinux-13d88ac5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f4da22719ffa/bzImage-13d88ac5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+26eedf...@syzkaller.appspotmail.com

executing program
BUG: memory leak
unreferenced object 0xffff8881009b40a8 (size 8):
comm "syz-executor225", pid 5035, jiffies 4294944336 (age 13.730s)
hex dump (first 8 bytes):
2e 00 00 00 00 00 00 00 ........
backtrace:
[<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
[<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
[<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
[<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
[<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62
[<ffffffff81d0438a>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
[<ffffffff81d0438a>] ovl_parse_param+0x70a/0xc70 fs/overlayfs/params.c:576
[<ffffffff8170542b>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
[<ffffffff81705556>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
[<ffffffff8170566f>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
[<ffffffff816dff08>] do_new_mount fs/namespace.c:3333 [inline]
[<ffffffff816dff08>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
[<ffffffff816e0b41>] do_mount fs/namespace.c:3677 [inline]
[<ffffffff816e0b41>] __do_sys_mount fs/namespace.c:3886 [inline]
[<ffffffff816e0b41>] __se_sys_mount fs/namespace.c:3863 [inline]
[<ffffffff816e0b41>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863
[<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
[<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: memory leak
unreferenced object 0xffff88814002d070 (size 8):
comm "syz-executor225", pid 5036, jiffies 4294944900 (age 8.090s)
hex dump (first 8 bytes):
2e 00 00 00 00 00 00 00 ........
backtrace:
[<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
[<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
[<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
[<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
[<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62
[<ffffffff81d0438a>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
[<ffffffff81d0438a>] ovl_parse_param+0x70a/0xc70 fs/overlayfs/params.c:576
[<ffffffff8170542b>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
[<ffffffff81705556>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
[<ffffffff8170566f>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
[<ffffffff816dff08>] do_new_mount fs/namespace.c:3333 [inline]
[<ffffffff816dff08>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
[<ffffffff816e0b41>] do_mount fs/namespace.c:3677 [inline]
[<ffffffff816e0b41>] __do_sys_mount fs/namespace.c:3886 [inline]
[<ffffffff816e0b41>] __se_sys_mount fs/namespace.c:3863 [inline]
[<ffffffff816e0b41>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863
[<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
[<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b



---
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[Edward Adam Davis]

please test memory leak in ovl_parse_param

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 13d88ac54ddd

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index ddab9ea267d1..735ae0db404a 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -530,6 +530,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
return 0;

out_put:
+ ctr->nr = nr;
ovl_reset_lowerdirs(ctx);

out_err:

[syzbot]

Hello,

syzbot tried to test the proposed patch but the build/boot failed:

fs/overlayfs/params.c:533:9: error: 'ctr' undeclared (first use in this function); did you mean 'ctx'?


Tested on:

commit: 13d88ac5 Merge tag 'vfs-6.7.fsid' of git://git.kernel...
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git

kernel config: https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=1723dc70e80000

[Amir Goldstein]

#syz test: https://github.com/amir73il/linux ovl-fixes

[syzbot]

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
memory leak in ovl_parse_param

BUG: memory leak
unreferenced object 0xffff88814002d0c8 (size 8):
comm "syz-executor.0", pid 5498, jiffies 4294944229 (age 12.660s)

hex dump (first 8 bytes):
2e 00 00 00 00 00 00 00 ........
backtrace:
[<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
[<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
[<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
[<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
[<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62

[<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
[<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
[<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
[<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
[<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
[<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
[<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
[<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
[<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
[<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
[<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863

[<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
[<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: memory leak

unreferenced object 0xffff8881009ec0c8 (size 8):
comm "syz-executor.0", pid 5752, jiffies 4294944765 (age 7.300s)

hex dump (first 8 bytes):
2e 00 00 00 00 00 00 00 ........
backtrace:
[<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
[<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
[<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
[<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
[<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62

[<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
[<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
[<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
[<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
[<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
[<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
[<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
[<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
[<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
[<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
[<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863

[<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
[<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

BUG: memory leak

unreferenced object 0xffff8881009ec0e0 (size 8):
comm "syz-executor.0", pid 5754, jiffies 4294944766 (age 7.290s)

hex dump (first 8 bytes):
2e 00 00 00 00 00 00 00 ........
backtrace:
[<ffffffff8163331d>] kmemleak_alloc_recursive include/linux/kmemleak.h:42 [inline]
[<ffffffff8163331d>] slab_post_alloc_hook mm/slab.h:766 [inline]
[<ffffffff8163331d>] slab_alloc_node mm/slub.c:3478 [inline]
[<ffffffff8163331d>] __kmem_cache_alloc_node+0x2dd/0x3f0 mm/slub.c:3517
[<ffffffff8157e57c>] __do_kmalloc_node mm/slab_common.c:1006 [inline]
[<ffffffff8157e57c>] __kmalloc_node_track_caller+0x4c/0x150 mm/slab_common.c:1027
[<ffffffff8156da4c>] kstrdup+0x3c/0x70 mm/util.c:62

[<ffffffff81d0424e>] ovl_parse_param_lowerdir fs/overlayfs/params.c:496 [inline]
[<ffffffff81d0424e>] ovl_parse_param+0x70e/0xc60 fs/overlayfs/params.c:576
[<ffffffff817053ab>] vfs_parse_fs_param+0xfb/0x190 fs/fs_context.c:146
[<ffffffff817054d6>] vfs_parse_fs_string+0x96/0xd0 fs/fs_context.c:188
[<ffffffff817055ef>] vfs_parse_monolithic_sep+0xdf/0x130 fs/fs_context.c:230
[<ffffffff816dfe88>] do_new_mount fs/namespace.c:3333 [inline]
[<ffffffff816dfe88>] path_mount+0xc48/0x10d0 fs/namespace.c:3664
[<ffffffff816e0ac1>] do_mount fs/namespace.c:3677 [inline]
[<ffffffff816e0ac1>] __do_sys_mount fs/namespace.c:3886 [inline]
[<ffffffff816e0ac1>] __se_sys_mount fs/namespace.c:3863 [inline]
[<ffffffff816e0ac1>] __x64_sys_mount+0x1a1/0x1f0 fs/namespace.c:3863

[<ffffffff84b67d8f>] do_syscall_x64 arch/x86/entry/common.c:51 [inline]
[<ffffffff84b67d8f>] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:82
[<ffffffff84c0008b>] entry_SYSCALL_64_after_hwframe+0x63/0x6b

Tested on:

commit: 3f653af2 ovl: fix memory leak in ovl_parse_param()
git tree: https://github.com/amir73il/linux ovl-fixes
console output: https://syzkaller.appspot.com/x/log.txt?x=13a07ea7680000

kernel config: https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.

[Edward Adam Davis]

please test memory leak in ovl_parse_param

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 13d88ac54ddd

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index ddab9ea267d1..735ae0db404a 100644
--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -530,6 +530,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
return 0;

out_put:

+ ctx->nr = nr;
ovl_reset_lowerdirs(ctx);

out_err:

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+26eedf...@syzkaller.appspotmail.com

Tested on:

commit: 13d88ac5 Merge tag 'vfs-6.7.fsid' of git://git.kernel...
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=11830270e80000

kernel config: https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

patch: https://syzkaller.appspot.com/x/patch.diff?x=10d85f38e80000

Note: testing is done by a robot and is best-effort only.

[Edward Adam Davis]

After failing to parse parameters in ovl_parse_param_lowerdir(), it is
necessary to update ctx->nr with the correct nr before using
ovl_reset_lowerdirs() to release l->name.

Reported-and-tested-by: syzbot+26eedf...@syzkaller.appspotmail.com
Signed-off-by: Edward Adam Davis <ead...@qq.com>
---
fs/overlayfs/params.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/fs/overlayfs/params.c b/fs/overlayfs/params.c
index ddab9ea267d1..1f73f0173015 100644

--- a/fs/overlayfs/params.c
+++ b/fs/overlayfs/params.c
@@ -530,6 +530,7 @@ static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
return 0;

out_put:
+ ctx->nr = nr;
ovl_reset_lowerdirs(ctx);

out_err:

--
2.25.1

[Amir Goldstein]

Thanks for the patch!

I prefer to fix it by eliminating the local vars instead of
syncing with them:

I've kept your commit message and tagged you as Co-authored-by:
https://github.com/amir73il/linux/commit/97d58994e880ccb19e1b9b935928538903fca41c

Thanks,
Amir.

[Amir Goldstein]

Please test take #2:

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+26eedf...@syzkaller.appspotmail.com

Tested on:

commit: 97d58994 ovl: fix memory leak in ovl_parse_param()

git tree: https://github.com/amir73il/linux ovl-fixes

console output: https://syzkaller.appspot.com/x/log.txt?x=12394b97680000

kernel config: https://syzkaller.appspot.com/x/.config?x=ecfdf78a410c834
dashboard link: https://syzkaller.appspot.com/bug?extid=26eedf3631650972f17c
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

Note: no patches were applied.