On 5/31/2018 1:57 PM, Eric W. Biederman wrote: > Casey Schaufler <casey@xxxxxxxxxxxxxxxx> writes: > >> On 5/31/2018 2:28 AM, CHANDAN VN wrote: >>> From: "sireesha.t" <sireesha.t@xxxxxxxxxxx> >>> >>> Leak is caused because smack_inode_getsecurity() is allocating memory >>> using kstrdup(). Though the security_release_secctx() is called, it >>> would not free the allocated memory. Calling security_release_secctx is >>> not relevant for this scenario as inode_getsecurity() does not provide a >>> "secctx". >>> >>> Similar fix has been mainlined: >>> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=57e7ba04d422c3d41c8426380303ec9b7533ded9 >>> >>> The fix is to replace the security_release_secctx() with a kfree() >>> >>> Below is the KMEMLEAK dump: >>> unreferenced object 0xffffffc025e11c80 (size 64): >>> comm "systemd-tmpfile", pid 2452, jiffies 4294894464 (age 235587.492s) >>> hex dump (first 32 bytes): >>> 53 79 73 74 65 6d 3a 3a 53 68 61 72 65 64 00 00 System::Shared.. >>> 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ >>> backtrace: >>> [<ffffff80081be770>] __save_stack_trace+0x28/0x34 >>> [<ffffff80081bedb8>] create_object+0x130/0x25c >>> [<ffffff80088c82f8>] kmemleak_alloc+0x30/0x5c >>> [<ffffff80081b3ef0>] __kmalloc_track_caller+0x1cc/0x2a8 >>> [<ffffff800818673c>] kstrdup+0x3c/0x6c >>> [<ffffff80082d78b0>] smack_inode_getsecurity+0xcc/0xec >>> [<ffffff80082d78f4>] smack_inode_getsecctx+0x24/0x44 >>> [<ffffff80082d5ea0>] security_inode_getsecctx+0x50/0x70 >>> [<ffffff800823bbcc>] kernfs_security_xattr_set+0x74/0xe0 >>> [<ffffff80081eafec>] __vfs_setxattr+0x74/0x90 >>> [<ffffff80081eb088>] __vfs_setxattr_noperm+0x80/0x1ac >>> [<ffffff80081eb238>] vfs_setxattr+0x84/0xac >>> [<ffffff80081eb374>] setxattr+0x114/0x178 >>> [<ffffff80081eb44c>] path_setxattr+0x74/0xb8 >>> [<ffffff80081ebdcc>] SyS_lsetxattr+0x10/0x1c >>> [<ffffff800808310c>] __sys_trace_return+0x0/0x4 >>> >>> Signed-off-by: sireesha.t <sireesha.t@xxxxxxxxxxx> >>> Signed-off-by: CHANDAN VN <chandan.vn@xxxxxxxxxxx> >> Why not: >> >> static int smack_inode_getsecctx(struct inode *inode, void **ctx, u32 *ctxlen) >> { >> - int len = 0; >> - len = smack_inode_getsecurity(inode, XATTR_SMACK_SUFFIX, ctx, true); >> + int len = smack_inode_getsecurity(inode, XATTR_SMACK_SUFFIX, ctx, false); >> > The practical difference here is the true vs the false in the call > to smack_inode_getsecurity? That is correct. The author of smack_inode_getsecctx() has a SELinux background and appears to have missed that Smack is careful not to allocate memory and make copies of labels when it doesn't need to. > >> if (len < 0) >> return len; >> > Eric > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
