memory leak in cap_inode_getsecurity

memory leak in cap_inode_getsecurity

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    0f1a7b3f timer-of: don't use conditional expression with m..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1329640d600000
kernel config:  https://syzkaller.appspot.com/x/.config?x=9d66badf12ef344c
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1107b513600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com

2019/10/03 14:00:37 executed programs: 36
2019/10/03 14:00:43 executed programs: 44
2019/10/03 14:00:49 executed programs: 63
BUG: memory leak
unreferenced object 0xffff8881202cb480 (size 32):
   comm "syz-executor.0", pid 7246, jiffies 4294946879 (age 14.010s)
   hex dump (first 32 bytes):
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
   backtrace:
     [<00000000a8379648>] kmemleak_alloc_recursive  
include/linux/kmemleak.h:43 [inline]
     [<00000000a8379648>] slab_post_alloc_hook mm/slab.h:586 [inline]
     [<00000000a8379648>] slab_alloc mm/slab.c:3319 [inline]
     [<00000000a8379648>] __do_kmalloc mm/slab.c:3653 [inline]
     [<00000000a8379648>] __kmalloc_track_caller+0x165/0x300 mm/slab.c:3670
     [<000000008858463c>] __do_krealloc mm/slab_common.c:1638 [inline]
     [<000000008858463c>] krealloc+0x7f/0xb0 mm/slab_common.c:1689
     [<0000000057f9eb8e>] vfs_getxattr_alloc+0x100/0x180 fs/xattr.c:289
     [<00000000c2154e30>] cap_inode_getsecurity+0x9c/0x2c0  
security/commoncap.c:389
     [<00000000b2664a09>] security_inode_getsecurity+0x4c/0x90  
security/security.c:1314
     [<00000000921624c0>] xattr_getsecurity fs/xattr.c:244 [inline]
     [<00000000921624c0>] vfs_getxattr+0xf2/0x1a0 fs/xattr.c:332
     [<000000001ff6977b>] getxattr+0x97/0x240 fs/xattr.c:538
     [<00000000b945681f>] path_getxattr+0x6b/0xc0 fs/xattr.c:566
     [<000000001a9d3fce>] __do_sys_getxattr fs/xattr.c:578 [inline]
     [<000000001a9d3fce>] __se_sys_getxattr fs/xattr.c:575 [inline]
     [<000000001a9d3fce>] __x64_sys_getxattr+0x28/0x30 fs/xattr.c:575
     [<000000002e998337>] do_syscall_64+0x73/0x1f0  
arch/x86/entry/common.c:290
     [<00000000f252aa21>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

Re: [syzbot] memory leak in cap_inode_getsecurity

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit:    6a010258447d Merge tag 'for-linus' of git://git.armlinux.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15883fee080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2a1dcc1942e30704
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1568846a080000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f5e536080000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com

executing program
BUG: memory leak
unreferenced object 0xffff88810f0ac060 (size 32):
  comm "syz-executor240", pid 3622, jiffies 4294961303 (age 14.040s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
  backtrace:
    [<ffffffff814c6ecd>] __do_krealloc mm/slab_common.c:1185 [inline]
    [<ffffffff814c6ecd>] krealloc+0x4d/0xb0 mm/slab_common.c:1218
    [<ffffffff8162625c>] vfs_getxattr_alloc+0x13c/0x1c0 fs/xattr.c:379
    [<ffffffff822374b2>] cap_inode_getsecurity+0xb2/0x500 security/commoncap.c:400
    [<ffffffff8223d88c>] security_inode_getsecurity+0x7c/0xb0 security/security.c:1441
    [<ffffffff81625a0a>] xattr_getsecurity fs/xattr.c:327 [inline]
    [<ffffffff81625a0a>] vfs_getxattr+0x22a/0x290 fs/xattr.c:423
    [<ffffffff81c0ab02>] ovl_xattr_get+0x62/0xa0 fs/overlayfs/inode.c:404
    [<ffffffff81624742>] __vfs_getxattr+0x72/0xa0 fs/xattr.c:401
    [<ffffffff82236f52>] cap_inode_need_killpriv+0x22/0x40 security/commoncap.c:301
    [<ffffffff8223d773>] security_inode_need_killpriv+0x23/0x60 security/security.c:1419
    [<ffffffff8161074e>] dentry_needs_remove_privs fs/inode.c:1992 [inline]
    [<ffffffff8161074e>] dentry_needs_remove_privs+0x4e/0xa0 fs/inode.c:1982
    [<ffffffff815cfead>] do_truncate+0x7d/0x130 fs/open.c:57
    [<ffffffff815d0169>] vfs_truncate+0x209/0x240 fs/open.c:111
    [<ffffffff815d0268>] do_sys_truncate.part.0+0xc8/0xe0 fs/open.c:134
    [<ffffffff815d0303>] do_sys_truncate fs/open.c:128 [inline]
    [<ffffffff815d0303>] __do_sys_truncate fs/open.c:146 [inline]
    [<ffffffff815d0303>] __se_sys_truncate fs/open.c:144 [inline]
    [<ffffffff815d0303>] __x64_sys_truncate+0x33/0x50 fs/open.c:144
    [<ffffffff845b1955>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
    [<ffffffff845b1955>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
    [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd

Re: [syzbot] memory leak in cap_inode_getsecurity

[Miklos Szeredi]

[-- Attachment #1: Type: text/plain, Size: 3041 bytes --]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master

On Sun, 31 Jul 2022 at 17:13, syzbot
<syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    6a010258447d Merge tag 'for-linus' of git://git.armlinux.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15883fee080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2a1dcc1942e30704
> dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1568846a080000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f5e536080000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com
>
> executing program
> BUG: memory leak
> unreferenced object 0xffff88810f0ac060 (size 32):
>   comm "syz-executor240", pid 3622, jiffies 4294961303 (age 14.040s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff814c6ecd>] __do_krealloc mm/slab_common.c:1185 [inline]
>     [<ffffffff814c6ecd>] krealloc+0x4d/0xb0 mm/slab_common.c:1218
>     [<ffffffff8162625c>] vfs_getxattr_alloc+0x13c/0x1c0 fs/xattr.c:379
>     [<ffffffff822374b2>] cap_inode_getsecurity+0xb2/0x500 security/commoncap.c:400
>     [<ffffffff8223d88c>] security_inode_getsecurity+0x7c/0xb0 security/security.c:1441
>     [<ffffffff81625a0a>] xattr_getsecurity fs/xattr.c:327 [inline]
>     [<ffffffff81625a0a>] vfs_getxattr+0x22a/0x290 fs/xattr.c:423
>     [<ffffffff81c0ab02>] ovl_xattr_get+0x62/0xa0 fs/overlayfs/inode.c:404
>     [<ffffffff81624742>] __vfs_getxattr+0x72/0xa0 fs/xattr.c:401
>     [<ffffffff82236f52>] cap_inode_need_killpriv+0x22/0x40 security/commoncap.c:301
>     [<ffffffff8223d773>] security_inode_need_killpriv+0x23/0x60 security/security.c:1419
>     [<ffffffff8161074e>] dentry_needs_remove_privs fs/inode.c:1992 [inline]
>     [<ffffffff8161074e>] dentry_needs_remove_privs+0x4e/0xa0 fs/inode.c:1982
>     [<ffffffff815cfead>] do_truncate+0x7d/0x130 fs/open.c:57
>     [<ffffffff815d0169>] vfs_truncate+0x209/0x240 fs/open.c:111
>     [<ffffffff815d0268>] do_sys_truncate.part.0+0xc8/0xe0 fs/open.c:134
>     [<ffffffff815d0303>] do_sys_truncate fs/open.c:128 [inline]
>     [<ffffffff815d0303>] __do_sys_truncate fs/open.c:146 [inline]
>     [<ffffffff815d0303>] __se_sys_truncate fs/open.c:144 [inline]
>     [<ffffffff815d0303>] __x64_sys_truncate+0x33/0x50 fs/open.c:144
>     [<ffffffff845b1955>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<ffffffff845b1955>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>     [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
>

[-- Attachment #2: fix-leak-in-cap_inode_getsecurity.patch --]
[-- Type: text/x-patch, Size: 1601 bytes --]

---
 security/commoncap.c |   18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -401,8 +401,8 @@ int cap_inode_getsecurity(struct user_na
 				      &tmpbuf, size, GFP_NOFS);
 	dput(dentry);
 
-	if (ret < 0 || !tmpbuf)
-		return ret;
+	if (ret < 0)
+		goto out_free;
 
 	fs_ns = inode->i_sb->s_user_ns;
 	cap = (struct vfs_cap_data *) tmpbuf;
@@ -412,7 +412,7 @@ int cap_inode_getsecurity(struct user_na
 		nscap = (struct vfs_ns_cap_data *) tmpbuf;
 		root = le32_to_cpu(nscap->rootid);
 	} else {
-		size = -EINVAL;
+		ret = -EINVAL;
 		goto out_free;
 	}
 
@@ -431,7 +431,7 @@ int cap_inode_getsecurity(struct user_na
 				/* v2 -> v3 conversion */
 				nscap = kzalloc(size, GFP_ATOMIC);
 				if (!nscap) {
-					size = -ENOMEM;
+					ret = -ENOMEM;
 					goto out_free;
 				}
 				nsmagic = VFS_CAP_REVISION_3;
@@ -447,11 +447,11 @@ int cap_inode_getsecurity(struct user_na
 			nscap->rootid = cpu_to_le32(mappedroot);
 			*buffer = nscap;
 		}
-		goto out_free;
+		goto success;
 	}
 
 	if (!rootid_owns_currentns(kroot)) {
-		size = -EOVERFLOW;
+		ret = -EOVERFLOW;
 		goto out_free;
 	}
 
@@ -462,7 +462,7 @@ int cap_inode_getsecurity(struct user_na
 			/* v3 -> v2 conversion */
 			cap = kzalloc(size, GFP_ATOMIC);
 			if (!cap) {
-				size = -ENOMEM;
+				ret = -ENOMEM;
 				goto out_free;
 			}
 			magic = VFS_CAP_REVISION_2;
@@ -477,9 +477,11 @@ int cap_inode_getsecurity(struct user_na
 		}
 		*buffer = cap;
 	}
+success:
+	ret = size;
 out_free:
 	kfree(tmpbuf);
-	return size;
+	return ret;
 }
 
 /**

Re: [syzbot] memory leak in cap_inode_getsecurity

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com

Tested on:

commit:         3d7cb6b0 Linux 5.19
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10aa0c2e080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5466231eb53fa40e
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10e003a6080000

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

Re: [syzbot] memory leak in cap_inode_getsecurity

[Miklos Szeredi]

[-- Attachment #1: Type: text/plain, Size: 3041 bytes --]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master

On Sun, 31 Jul 2022 at 17:13, syzbot
<syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    6a010258447d Merge tag 'for-linus' of git://git.armlinux.o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=15883fee080000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=2a1dcc1942e30704
> dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1568846a080000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f5e536080000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com
>
> executing program
> BUG: memory leak
> unreferenced object 0xffff88810f0ac060 (size 32):
>   comm "syz-executor240", pid 3622, jiffies 4294961303 (age 14.040s)
>   hex dump (first 32 bytes):
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>     00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>   backtrace:
>     [<ffffffff814c6ecd>] __do_krealloc mm/slab_common.c:1185 [inline]
>     [<ffffffff814c6ecd>] krealloc+0x4d/0xb0 mm/slab_common.c:1218
>     [<ffffffff8162625c>] vfs_getxattr_alloc+0x13c/0x1c0 fs/xattr.c:379
>     [<ffffffff822374b2>] cap_inode_getsecurity+0xb2/0x500 security/commoncap.c:400
>     [<ffffffff8223d88c>] security_inode_getsecurity+0x7c/0xb0 security/security.c:1441
>     [<ffffffff81625a0a>] xattr_getsecurity fs/xattr.c:327 [inline]
>     [<ffffffff81625a0a>] vfs_getxattr+0x22a/0x290 fs/xattr.c:423
>     [<ffffffff81c0ab02>] ovl_xattr_get+0x62/0xa0 fs/overlayfs/inode.c:404
>     [<ffffffff81624742>] __vfs_getxattr+0x72/0xa0 fs/xattr.c:401
>     [<ffffffff82236f52>] cap_inode_need_killpriv+0x22/0x40 security/commoncap.c:301
>     [<ffffffff8223d773>] security_inode_need_killpriv+0x23/0x60 security/security.c:1419
>     [<ffffffff8161074e>] dentry_needs_remove_privs fs/inode.c:1992 [inline]
>     [<ffffffff8161074e>] dentry_needs_remove_privs+0x4e/0xa0 fs/inode.c:1982
>     [<ffffffff815cfead>] do_truncate+0x7d/0x130 fs/open.c:57
>     [<ffffffff815d0169>] vfs_truncate+0x209/0x240 fs/open.c:111
>     [<ffffffff815d0268>] do_sys_truncate.part.0+0xc8/0xe0 fs/open.c:134
>     [<ffffffff815d0303>] do_sys_truncate fs/open.c:128 [inline]
>     [<ffffffff815d0303>] __do_sys_truncate fs/open.c:146 [inline]
>     [<ffffffff815d0303>] __se_sys_truncate fs/open.c:144 [inline]
>     [<ffffffff815d0303>] __x64_sys_truncate+0x33/0x50 fs/open.c:144
>     [<ffffffff845b1955>] do_syscall_x64 arch/x86/entry/common.c:50 [inline]
>     [<ffffffff845b1955>] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
>     [<ffffffff84600087>] entry_SYSCALL_64_after_hwframe+0x63/0xcd
>
>

[-- Attachment #2: vfs_getxattr_alloc-dont-allocate-buf-on-failure.patch --]
[-- Type: text/x-patch, Size: 384 bytes --]

---
 fs/xattr.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -383,7 +383,10 @@ vfs_getxattr_alloc(struct user_namespace
 	}
 
 	error = handler->get(handler, dentry, inode, name, value, error);
-	*xattr_value = value;
+	if (error < 0 && value != *xattr_value)
+		kfree(value);
+	else
+		*xattr_value = value;
 	return error;
 }
 

Re: [syzbot] memory leak in cap_inode_getsecurity

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com

Tested on:

commit:         3d7cb6b0 Linux 5.19
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14385261080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=5466231eb53fa40e
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=14edd10e080000

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

Re: memory leak in cap_inode_getsecurity

[Miklos Szeredi]

[-- Attachment #1: Type: text/plain, Size: 3137 bytes --]

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master

On Thu, 3 Oct 2019 at 21:59, syzbot
<syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following crash on:
>
> HEAD commit:    0f1a7b3f timer-of: don't use conditional expression with m..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=1329640d600000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=9d66badf12ef344c
> dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1107b513600000
>
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com
>
> 2019/10/03 14:00:37 executed programs: 36
> 2019/10/03 14:00:43 executed programs: 44
> 2019/10/03 14:00:49 executed programs: 63
> BUG: memory leak
> unreferenced object 0xffff8881202cb480 (size 32):
>    comm "syz-executor.0", pid 7246, jiffies 4294946879 (age 14.010s)
>    hex dump (first 32 bytes):
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>      00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
>    backtrace:
>      [<00000000a8379648>] kmemleak_alloc_recursive
> include/linux/kmemleak.h:43 [inline]
>      [<00000000a8379648>] slab_post_alloc_hook mm/slab.h:586 [inline]
>      [<00000000a8379648>] slab_alloc mm/slab.c:3319 [inline]
>      [<00000000a8379648>] __do_kmalloc mm/slab.c:3653 [inline]
>      [<00000000a8379648>] __kmalloc_track_caller+0x165/0x300 mm/slab.c:3670
>      [<000000008858463c>] __do_krealloc mm/slab_common.c:1638 [inline]
>      [<000000008858463c>] krealloc+0x7f/0xb0 mm/slab_common.c:1689
>      [<0000000057f9eb8e>] vfs_getxattr_alloc+0x100/0x180 fs/xattr.c:289
>      [<00000000c2154e30>] cap_inode_getsecurity+0x9c/0x2c0
> security/commoncap.c:389
>      [<00000000b2664a09>] security_inode_getsecurity+0x4c/0x90
> security/security.c:1314
>      [<00000000921624c0>] xattr_getsecurity fs/xattr.c:244 [inline]
>      [<00000000921624c0>] vfs_getxattr+0xf2/0x1a0 fs/xattr.c:332
>      [<000000001ff6977b>] getxattr+0x97/0x240 fs/xattr.c:538
>      [<00000000b945681f>] path_getxattr+0x6b/0xc0 fs/xattr.c:566
>      [<000000001a9d3fce>] __do_sys_getxattr fs/xattr.c:578 [inline]
>      [<000000001a9d3fce>] __se_sys_getxattr fs/xattr.c:575 [inline]
>      [<000000001a9d3fce>] __x64_sys_getxattr+0x28/0x30 fs/xattr.c:575
>      [<000000002e998337>] do_syscall_64+0x73/0x1f0
> arch/x86/entry/common.c:290
>      [<00000000f252aa21>] entry_SYSCALL_64_after_hwframe+0x44/0xa9
>
>
>
> ---
> This bug is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@googlegroups.com.
>
> syzbot will keep track of this bug report. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
> syzbot can test patches for this bug, for details see:
> https://goo.gl/tpsmEJ#testing-patches

[-- Attachment #2: vfs_getxattr_alloc-dont-allocate-buf-on-failure.patch --]
[-- Type: text/x-patch, Size: 1091 bytes --]

From: Miklos Szeredi <mszeredi@redhat.com>
Subject: vfs_getxattr_alloc(): don't allocate buf on failure

Some callers of vfs_getxattr_alloc() assume that on failure the allocated
buffer does not need to be freed.

Callers could be fixed, but fixing the semantics of vfs_getxattr_alloc() is
simpler and makes sure that this class of bugs does not occur again.

If this was called in a loop (i.e. xattr_value contains an already
allocated buffer), then caller will still need to clean up after an error.

Reported-and-tested-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com
Fixes: 1601fbad2b14 ("xattr: define vfs_getxattr_alloc and vfs_xattr_cmp")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/xattr.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/xattr.c
+++ b/fs/xattr.c
@@ -383,7 +383,10 @@ vfs_getxattr_alloc(struct user_namespace
 	}
 
 	error = handler->get(handler, dentry, inode, name, value, error);
-	*xattr_value = value;
+	if (error < 0 && *xattr_value == NULL)
+		kfree(value);
+	else
+		*xattr_value = value;
 	return error;
 }
 

Re: [syzbot] memory leak in cap_inode_getsecurity

[syzbot]

Hello,

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

Reported-and-tested-by: syzbot+942d5390db2d9624ced8@syzkaller.appspotmail.com

Tested on:

commit:         e2b54210 Merge tag 'flexible-array-transformations-UAP..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12c050a2080000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f5367bd9b8d9fa72
dashboard link: https://syzkaller.appspot.com/bug?extid=942d5390db2d9624ced8
compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
patch:          https://syzkaller.appspot.com/x/patch.diff?x=17a74536080000

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