mainline inclusion from mainline-v7.2-rc5 commit f8cf09a53a0dc1da298e9dd0ba5f21710cf119d6 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/19918 CVE: CVE-2026-93787 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- cifs_filldir() copies the entry name out of an SMB1 TRANS2_FIND_FIRST / FIND_NEXT response using a length (de.namelen) supplied by the server. The kmalloc'd SMB response buffer is bounded, but nothing checks that de.name + de.namelen still lies inside that buffer before the eventual filldir64() -> verify_dirent_name() -> memchr() reads namelen bytes. A hostile SMB1 server that returns an oversized FileNameLength in a directory entry therefore causes memchr() to read past the end of the response slab buffer. Reachable from any user who can list a directory on a CIFS mount served by an attacker-controlled server (getdents64() on the mounted directory): BUG: KASAN: slab-out-of-bounds in memchr+0x71/0x80 Read of size 1 at addr ffff88800e0640cc by task poc/115 Call Trace: dump_stack_lvl+0x64/0x80 print_report+0xce/0x620 kasan_report+0xec/0x120 memchr+0x71/0x80 filldir64+0x4c/0x6a0 cifs_filldir.constprop.0+0x9bb/0x1e00 cifs_readdir+0x2101/0x3380 iterate_dir+0x19c/0x520 __x64_sys_getdents64+0x126/0x210 do_syscall_64+0x107/0x5a0 entry_SYSCALL_64_after_hwframe+0x77/0x7f Pass the end-of-response pointer down to cifs_filldir() and reject entries whose name would extend past that boundary. This bug was discovered by Artiphishell's vTriage pipeline, which generated a userspace reproducer (an emulated hostile SMB1 server plus a getdents64() client) that reliably triggers the KASAN report on an unpatched kernel. The fix below was drafted with the Claude coding assistant; a userspace reproducer is available on request. Assisted-by: Claude:claude-opus-4-7 Signed-off-by: Jay Vadayath <jay@artiphishell.com> Signed-off-by: Steve French <stfrench@microsoft.com> Conflicts: fs/cifs/readdir.c [The target tree keeps the CIFS client under fs/cifs/ and cifs_filldir() has no struct cached_fid *cfid parameter yet, so only the new end_of_smb argument was added and passed from cifs_readdir().] Signed-off-by: Ran Hongyun <ranhongyun1@huawei.com> --- fs/cifs/readdir.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c index a7a9391214c1..3db39364ba55 100644 --- a/fs/cifs/readdir.c +++ b/fs/cifs/readdir.c @@ -835,7 +835,8 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos, static int cifs_filldir(char *find_entry, struct file *file, struct dir_context *ctx, - char *scratch_buf, unsigned int max_len) + char *scratch_buf, unsigned int max_len, + char *end_of_smb) { struct cifsFileInfo *file_info = file->private_data; struct super_block *sb = file_inode(file)->i_sb; @@ -857,6 +858,11 @@ static int cifs_filldir(char *find_entry, struct file *file, return -EINVAL; } + if (de.name + de.namelen > end_of_smb) { + cifs_dbg(VFS, "search entry name extends past end of SMB\n"); + return -EINVAL; + } + /* skip . and .. since we added them first */ if (cifs_entry_is_dot(&de, file_info->srch_inf.unicode)) return 0; @@ -1020,7 +1026,7 @@ int cifs_readdir(struct file *file, struct dir_context *ctx) */ *tmp_buf = 0; rc = cifs_filldir(current_entry, file, ctx, - tmp_buf, max_len); + tmp_buf, max_len, end_of_smb); if (rc) { if (rc > 0) rc = 0; -- 2.52.0