* FAILED: patch "[PATCH] smb: client: fix use-after-free infoleak via the readdir" failed to apply to 5.15-stable tree
@ 2026-11-04 13:36 gregkh
2026-11-04 19:45 ` [PATCH 5.15.y 1/3] smb: client: fix warning in CIFSFindFirst() Sasha Levin
0 siblings, 1 reply; 4+ messages in thread
From: gregkh @ 2026-11-04 13:36 UTC (permalink / raw)
To: diego, dhowells, pc; +Cc: stable
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 59131dd72f62b198fc9ea1489ad9d3573154f684
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026110403-submersed-uncloak-dc0a@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 59131dd72f62b198fc9ea1489ad9d3573154f684 Mon Sep 17 00:00:00 2001
From: Diego Oliva <diego@bynar.io>
Date: Tue, 29 Sep 2026 10:16:30 +0100
Subject: [PATCH] smb: client: fix use-after-free infoleak via the readdir
resume name
CIFSFindNext() copies the resume name that cifs_save_resume_key()
recorded from the last entry of the previous response into its request;
psrch_inf->presume_name points into the response buffer that entry came
from, and nothing ever clears it. find_cifs_entry() records a new
name only from a response with a usable last entry, and cifs_readdir()
only from an entry it walks to, so a response that carries no entries
and leaves last_entry NULL, because CIFSFindFirst() or CIFSFindNext()
rejected LastNameOffset, refreshes neither and presume_name keeps
pointing into the previous response. That buffer has already been
released: by CIFSFindNext() before it installs the new response, or by
find_cifs_entry() when it rewinds the search, which does not drop the
name either and can then fail in initiate_cifs_search() before a new
response replaces it. The next CIFSFindNext() then copies up to
PATH_MAX - 1 bytes of the resume name out of the released buffer into
its request and sends them to the server: a use-after-free read
that leaks kernel memory to a malicious or compromised server, which
can provoke it with a single FindNext response that carries no entries
and a LastNameOffset above CIFSMaxBufSize, which is all the existing
check rejects.
With KASAN enabled, a server that answers a listing that way gives:
CIFS: VFS: ignoring corrupt resume name
==================================================================
BUG: KASAN: slab-use-after-free in CIFSFindNext+0x8ca/0x14c0
Read of size 4080 at addr ffff88807c823f98 by task ls/83
CPU: 0 UID: 0 PID: 83 Comm: ls Tainted: G B 7.3.0-rc4-00457-gf14572c203d5 #69 PREEMPT(lazy)
Tainted: [B]=BAD_PAGE
Call Trace:
<TASK>
kasan_report+0xdf/0x1a0
kasan_check_range+0x10f/0x1e0
__asan_memcpy+0x23/0x60
CIFSFindNext+0x8ca/0x14c0
cifs_readdir+0xf51/0x29c0
iterate_dir+0x1c0/0x570
__x64_sys_getdents64+0x133/0x270
do_syscall_64+0x109/0x5d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
Allocated by task 83 on cpu 1 at 13.497119s:
cifs_buf_get+0x36/0x90
smb_init+0x4f/0x110
CIFSFindNext+0xf7/0x14c0
cifs_readdir+0xf51/0x29c0
Freed by task 83 on cpu 0 at 13.584018s:
cifs_buf_release+0x41/0x80
CIFSFindNext+0xfce/0x14c0
cifs_readdir+0xf51/0x29c0
The buggy address is located 16280 bytes inside of
freed 16588-byte region [ffff88807c820000, ffff88807c8240cc)
==================================================================
The same memcpy() first reads past the end of that object while it is
still live, a slab-out-of-bounds read that the following patches
bound; that is the taint the report above carries.
SMB1 is not negotiated by default; reaching this code requires an
explicit vers=1.0 mount.
Clear presume_name and resume_name_len whenever a new response is
installed and when the rewind path releases the search buffer, so that
the name never outlives the buffer it points into, and reset
resume_key with them, since it was taken from the same entry and would
otherwise be sent with an empty name. A response without a usable
last entry then continues the search with an empty resume name rather
than a stale one; CIFSFindNext() skips the copy of a zero-length name
so that it never runs on the NULL pointer.
The next patch in the series leaves last_entry NULL for a response
that carries no entries, and bounds LastNameOffset against the
received response rather than against CIFSMaxBufSize. Responses that
are given a last entry today then take the path fixed here, so that
patch must not be applied without this one.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: b77d753c413e ("[CIFS] Check that last search entry resume key is valid")
Cc: stable@vger.kernel.org
Assisted-by: Bynario AI
Signed-off-by: Diego Oliva <diego@bynar.io>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
diff --git a/fs/smb/client/cifssmb.c b/fs/smb/client/cifssmb.c
index 6dddbd84b93b..95f339f48ad7 100644
--- a/fs/smb/client/cifssmb.c
+++ b/fs/smb/client/cifssmb.c
@@ -4543,6 +4543,9 @@ CIFSFindFirst(const unsigned int xid, struct cifs_tcon *tcon,
psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
psrch_inf->index_of_last_entry = 2 /* skip . and .. */ +
psrch_inf->entries_in_buffer;
+ psrch_inf->presume_name = NULL;
+ psrch_inf->resume_name_len = 0;
+ psrch_inf->resume_key = 0;
lnoff = le16_to_cpu(parms->LastNameOffset);
if (CIFSMaxBufSize < lnoff) {
cifs_dbg(VFS, "ignoring corrupt resume name\n");
@@ -4607,7 +4610,10 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
name_len = psrch_inf->resume_name_len;
params += name_len;
if (name_len < PATH_MAX) {
- memcpy(pSMB->ResumeFileName, psrch_inf->presume_name, name_len);
+ if (name_len) {
+ memcpy(pSMB->ResumeFileName,
+ psrch_inf->presume_name, name_len);
+ }
byte_count += name_len;
/* 14 byte parm len above enough for 2 byte null terminator */
pSMB->ResumeFileName[name_len] = 0;
@@ -4662,6 +4668,9 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
psrch_inf->endOfSearch = !!parms->EndofSearch;
psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
psrch_inf->index_of_last_entry += psrch_inf->entries_in_buffer;
+ psrch_inf->presume_name = NULL;
+ psrch_inf->resume_name_len = 0;
+ psrch_inf->resume_key = 0;
lnoff = le16_to_cpu(parms->LastNameOffset);
if (CIFSMaxBufSize < lnoff) {
cifs_dbg(VFS, "ignoring corrupt resume name\n");
diff --git a/fs/smb/client/readdir.c b/fs/smb/client/readdir.c
index 9530e5b01564..6ab4e687c3e4 100644
--- a/fs/smb/client/readdir.c
+++ b/fs/smb/client/readdir.c
@@ -752,6 +752,9 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
cfile->srch_inf.ntwrk_buf_start = NULL;
cfile->srch_inf.srch_entries_start = NULL;
cfile->srch_inf.last_entry = NULL;
+ cfile->srch_inf.presume_name = NULL;
+ cfile->srch_inf.resume_name_len = 0;
+ cfile->srch_inf.resume_key = 0;
}
rc = initiate_cifs_search(xid, file, full_path);
if (rc) {
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 5.15.y 1/3] smb: client: fix warning in CIFSFindFirst()
2026-11-04 13:36 FAILED: patch "[PATCH] smb: client: fix use-after-free infoleak via the readdir" failed to apply to 5.15-stable tree gregkh
@ 2026-11-04 19:45 ` Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 2/3] smb: client: fix warning in CIFSFindNext() Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name Sasha Levin
0 siblings, 2 replies; 4+ messages in thread
From: Sasha Levin @ 2026-11-04 19:45 UTC (permalink / raw)
To: stable; +Cc: Paulo Alcantara, Steve French, Sasha Levin
From: Paulo Alcantara <pc@manguebit.com>
[ Upstream commit 032137fe136a6073dcc699ee15fa3fd05fd77f21 ]
This fixes the following warning reported by kernel test robot
fs/smb/client/cifssmb.c:4089 CIFSFindFirst() warn: missing error
code? 'rc'
Link: https://lore.kernel.org/all/202306170124.CtQqzf0I-lkp@intel.com/
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Stable-dep-of: 59131dd72f62 ("smb: client: fix use-after-free infoleak via the readdir resume name")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/cifssmb.c | 94 +++++++++++++++++++++--------------------------
1 file changed, 42 insertions(+), 52 deletions(-)
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 11a400663b9f2..36ed6906066ea 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4333,11 +4333,12 @@ CIFSFindFirst(const unsigned int xid, struct cifs_tcon *tcon,
TRANSACTION2_FFIRST_REQ *pSMB = NULL;
TRANSACTION2_FFIRST_RSP *pSMBr = NULL;
T2_FFIRST_RSP_PARMS *parms;
- int rc = 0;
+ struct nls_table *nls_codepage;
+ unsigned int lnoff;
+ __u16 params, byte_count;
int bytes_returned = 0;
int name_len, remap;
- __u16 params, byte_count;
- struct nls_table *nls_codepage;
+ int rc = 0;
cifs_dbg(FYI, "In FindFirst for %s\n", searchName);
@@ -4428,63 +4429,52 @@ CIFSFindFirst(const unsigned int xid, struct cifs_tcon *tcon,
(struct smb_hdr *) pSMBr, &bytes_returned, 0);
cifs_stats_inc(&tcon->stats.cifs_stats.num_ffirst);
- if (rc) {/* BB add logic to retry regular search if Unix search
- rejected unexpectedly by server */
- /* BB Add code to handle unsupported level rc */
+ if (rc) {
+ /*
+ * BB: add logic to retry regular search if Unix search rejected
+ * unexpectedly by server.
+ */
+ /* BB: add code to handle unsupported level rc */
cifs_dbg(FYI, "Error in FindFirst = %d\n", rc);
-
cifs_buf_release(pSMB);
-
- /* BB eventually could optimize out free and realloc of buf */
- /* for this case */
+ /*
+ * BB: eventually could optimize out free and realloc of buf for
+ * this case.
+ */
if (rc == -EAGAIN)
goto findFirstRetry;
- } else { /* decode response */
- /* BB remember to free buffer if error BB */
- rc = validate_t2((struct smb_t2_rsp *)pSMBr);
- if (rc == 0) {
- unsigned int lnoff;
-
- if (pSMBr->hdr.Flags2 & SMBFLG2_UNICODE)
- psrch_inf->unicode = true;
- else
- psrch_inf->unicode = false;
-
- psrch_inf->ntwrk_buf_start = (char *)pSMBr;
- psrch_inf->smallBuf = false;
- psrch_inf->srch_entries_start =
- (char *) &pSMBr->hdr.Protocol +
- le16_to_cpu(pSMBr->t2.DataOffset);
- parms = (T2_FFIRST_RSP_PARMS *)((char *) &pSMBr->hdr.Protocol +
- le16_to_cpu(pSMBr->t2.ParameterOffset));
-
- if (parms->EndofSearch)
- psrch_inf->endOfSearch = true;
- else
- psrch_inf->endOfSearch = false;
+ return rc;
+ }
+ /* decode response */
+ rc = validate_t2((struct smb_t2_rsp *)pSMBr);
+ if (rc) {
+ cifs_buf_release(pSMB);
+ return rc;
+ }
- psrch_inf->entries_in_buffer =
- le16_to_cpu(parms->SearchCount);
- psrch_inf->index_of_last_entry = 2 /* skip . and .. */ +
- psrch_inf->entries_in_buffer;
- lnoff = le16_to_cpu(parms->LastNameOffset);
- if (CIFSMaxBufSize < lnoff) {
- cifs_dbg(VFS, "ignoring corrupt resume name\n");
- psrch_inf->last_entry = NULL;
- return rc;
- }
+ psrch_inf->unicode = !!(pSMBr->hdr.Flags2 & SMBFLG2_UNICODE);
+ psrch_inf->ntwrk_buf_start = (char *)pSMBr;
+ psrch_inf->smallBuf = false;
+ psrch_inf->srch_entries_start = (char *)&pSMBr->hdr.Protocol +
+ le16_to_cpu(pSMBr->t2.DataOffset);
- psrch_inf->last_entry = psrch_inf->srch_entries_start +
- lnoff;
+ parms = (T2_FFIRST_RSP_PARMS *)((char *)&pSMBr->hdr.Protocol +
+ le16_to_cpu(pSMBr->t2.ParameterOffset));
+ psrch_inf->endOfSearch = !!parms->EndofSearch;
- if (pnetfid)
- *pnetfid = parms->SearchHandle;
- } else {
- cifs_buf_release(pSMB);
- }
+ psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
+ psrch_inf->index_of_last_entry = 2 /* skip . and .. */ +
+ psrch_inf->entries_in_buffer;
+ lnoff = le16_to_cpu(parms->LastNameOffset);
+ if (CIFSMaxBufSize < lnoff) {
+ cifs_dbg(VFS, "ignoring corrupt resume name\n");
+ psrch_inf->last_entry = NULL;
+ } else {
+ psrch_inf->last_entry = psrch_inf->srch_entries_start + lnoff;
+ if (pnetfid)
+ *pnetfid = parms->SearchHandle;
}
-
- return rc;
+ return 0;
}
int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 5.15.y 2/3] smb: client: fix warning in CIFSFindNext()
2026-11-04 19:45 ` [PATCH 5.15.y 1/3] smb: client: fix warning in CIFSFindFirst() Sasha Levin
@ 2026-11-04 19:45 ` Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2026-11-04 19:45 UTC (permalink / raw)
To: stable; +Cc: Paulo Alcantara, Steve French, Sasha Levin
From: Paulo Alcantara <pc@manguebit.com>
[ Upstream commit 215533f888dcf18f7cfbbf520bdd52e67ac6265a ]
This fixes the following warning reported by kernel test robot
fs/smb/client/cifssmb.c:4216 CIFSFindNext() warn: missing error
code? 'rc'
Link: https://lore.kernel.org/all/202306170124.CtQqzf0I-lkp@intel.com/
Signed-off-by: Paulo Alcantara (SUSE) <pc@manguebit.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Stable-dep-of: 59131dd72f62 ("smb: client: fix use-after-free infoleak via the readdir resume name")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/cifssmb.c | 111 +++++++++++++++++++++-------------------------
1 file changed, 51 insertions(+), 60 deletions(-)
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 36ed6906066ea..5b1fb3216f238 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4484,11 +4484,12 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
TRANSACTION2_FNEXT_REQ *pSMB = NULL;
TRANSACTION2_FNEXT_RSP *pSMBr = NULL;
T2_FNEXT_RSP_PARMS *parms;
- char *response_data;
- int rc = 0;
- int bytes_returned;
unsigned int name_len;
+ unsigned int lnoff;
__u16 params, byte_count;
+ char *response_data;
+ int bytes_returned;
+ int rc = 0;
cifs_dbg(FYI, "In FindNext\n");
@@ -4533,8 +4534,8 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
pSMB->ResumeFileName[name_len] = 0;
pSMB->ResumeFileName[name_len+1] = 0;
} else {
- rc = -EINVAL;
- goto FNext2_err_exit;
+ cifs_buf_release(pSMB);
+ return -EINVAL;
}
byte_count = params + 1 /* pad */ ;
pSMB->TotalParameterCount = cpu_to_le16(params);
@@ -4545,71 +4546,61 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
rc = SendReceive(xid, tcon->ses, (struct smb_hdr *) pSMB,
(struct smb_hdr *) pSMBr, &bytes_returned, 0);
cifs_stats_inc(&tcon->stats.cifs_stats.num_fnext);
+
if (rc) {
+ cifs_buf_release(pSMB);
if (rc == -EBADF) {
psrch_inf->endOfSearch = true;
- cifs_buf_release(pSMB);
rc = 0; /* search probably was closed at end of search*/
- } else
+ } else {
cifs_dbg(FYI, "FindNext returned = %d\n", rc);
- } else { /* decode response */
- rc = validate_t2((struct smb_t2_rsp *)pSMBr);
-
- if (rc == 0) {
- unsigned int lnoff;
-
- /* BB fixme add lock for file (srch_info) struct here */
- if (pSMBr->hdr.Flags2 & SMBFLG2_UNICODE)
- psrch_inf->unicode = true;
- else
- psrch_inf->unicode = false;
- response_data = (char *) &pSMBr->hdr.Protocol +
- le16_to_cpu(pSMBr->t2.ParameterOffset);
- parms = (T2_FNEXT_RSP_PARMS *)response_data;
- response_data = (char *)&pSMBr->hdr.Protocol +
- le16_to_cpu(pSMBr->t2.DataOffset);
- if (psrch_inf->smallBuf)
- cifs_small_buf_release(
- psrch_inf->ntwrk_buf_start);
- else
- cifs_buf_release(psrch_inf->ntwrk_buf_start);
- psrch_inf->srch_entries_start = response_data;
- psrch_inf->ntwrk_buf_start = (char *)pSMB;
- psrch_inf->smallBuf = false;
- if (parms->EndofSearch)
- psrch_inf->endOfSearch = true;
- else
- psrch_inf->endOfSearch = false;
- psrch_inf->entries_in_buffer =
- le16_to_cpu(parms->SearchCount);
- psrch_inf->index_of_last_entry +=
- psrch_inf->entries_in_buffer;
- lnoff = le16_to_cpu(parms->LastNameOffset);
- if (CIFSMaxBufSize < lnoff) {
- cifs_dbg(VFS, "ignoring corrupt resume name\n");
- psrch_inf->last_entry = NULL;
- return rc;
- } else
- psrch_inf->last_entry =
- psrch_inf->srch_entries_start + lnoff;
-
-/* cifs_dbg(FYI, "fnxt2 entries in buf %d index_of_last %d\n",
- psrch_inf->entries_in_buffer, psrch_inf->index_of_last_entry); */
-
- /* BB fixme add unlock here */
}
+ return rc;
+ }
+ /* decode response */
+ rc = validate_t2((struct smb_t2_rsp *)pSMBr);
+ if (rc) {
+ cifs_buf_release(pSMB);
+ return rc;
}
+ /* BB fixme add lock for file (srch_info) struct here */
+ psrch_inf->unicode = !!(pSMBr->hdr.Flags2 & SMBFLG2_UNICODE);
+ response_data = (char *)&pSMBr->hdr.Protocol +
+ le16_to_cpu(pSMBr->t2.ParameterOffset);
+ parms = (T2_FNEXT_RSP_PARMS *)response_data;
+ response_data = (char *)&pSMBr->hdr.Protocol +
+ le16_to_cpu(pSMBr->t2.DataOffset);
- /* BB On error, should we leave previous search buf (and count and
- last entry fields) intact or free the previous one? */
+ if (psrch_inf->smallBuf)
+ cifs_small_buf_release(psrch_inf->ntwrk_buf_start);
+ else
+ cifs_buf_release(psrch_inf->ntwrk_buf_start);
- /* Note: On -EAGAIN error only caller can retry on handle based calls
- since file handle passed in no longer valid */
-FNext2_err_exit:
- if (rc != 0)
- cifs_buf_release(pSMB);
- return rc;
+ psrch_inf->srch_entries_start = response_data;
+ psrch_inf->ntwrk_buf_start = (char *)pSMB;
+ psrch_inf->smallBuf = false;
+ psrch_inf->endOfSearch = !!parms->EndofSearch;
+ psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
+ psrch_inf->index_of_last_entry += psrch_inf->entries_in_buffer;
+ lnoff = le16_to_cpu(parms->LastNameOffset);
+ if (CIFSMaxBufSize < lnoff) {
+ cifs_dbg(VFS, "ignoring corrupt resume name\n");
+ psrch_inf->last_entry = NULL;
+ } else {
+ psrch_inf->last_entry =
+ psrch_inf->srch_entries_start + lnoff;
+ }
+ /* BB fixme add unlock here */
+
+ /*
+ * BB: On error, should we leave previous search buf
+ * (and count and last entry fields) intact or free the previous one?
+ *
+ * Note: On -EAGAIN error only caller can retry on handle based calls
+ * since file handle passed in no longer valid.
+ */
+ return 0;
}
int
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* [PATCH 5.15.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name
2026-11-04 19:45 ` [PATCH 5.15.y 1/3] smb: client: fix warning in CIFSFindFirst() Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 2/3] smb: client: fix warning in CIFSFindNext() Sasha Levin
@ 2026-11-04 19:45 ` Sasha Levin
1 sibling, 0 replies; 4+ messages in thread
From: Sasha Levin @ 2026-11-04 19:45 UTC (permalink / raw)
To: stable; +Cc: Diego Oliva, David Howells, Paulo Alcantara, Sasha Levin
From: Diego Oliva <diego@bynar.io>
[ Upstream commit 59131dd72f62b198fc9ea1489ad9d3573154f684 ]
CIFSFindNext() copies the resume name that cifs_save_resume_key()
recorded from the last entry of the previous response into its request;
psrch_inf->presume_name points into the response buffer that entry came
from, and nothing ever clears it. find_cifs_entry() records a new
name only from a response with a usable last entry, and cifs_readdir()
only from an entry it walks to, so a response that carries no entries
and leaves last_entry NULL, because CIFSFindFirst() or CIFSFindNext()
rejected LastNameOffset, refreshes neither and presume_name keeps
pointing into the previous response. That buffer has already been
released: by CIFSFindNext() before it installs the new response, or by
find_cifs_entry() when it rewinds the search, which does not drop the
name either and can then fail in initiate_cifs_search() before a new
response replaces it. The next CIFSFindNext() then copies up to
PATH_MAX - 1 bytes of the resume name out of the released buffer into
its request and sends them to the server: a use-after-free read
that leaks kernel memory to a malicious or compromised server, which
can provoke it with a single FindNext response that carries no entries
and a LastNameOffset above CIFSMaxBufSize, which is all the existing
check rejects.
With KASAN enabled, a server that answers a listing that way gives:
CIFS: VFS: ignoring corrupt resume name
==================================================================
BUG: KASAN: slab-use-after-free in CIFSFindNext+0x8ca/0x14c0
Read of size 4080 at addr ffff88807c823f98 by task ls/83
CPU: 0 UID: 0 PID: 83 Comm: ls Tainted: G B 7.3.0-rc4-00457-gf14572c203d5 #69 PREEMPT(lazy)
Tainted: [B]=BAD_PAGE
Call Trace:
<TASK>
kasan_report+0xdf/0x1a0
kasan_check_range+0x10f/0x1e0
__asan_memcpy+0x23/0x60
CIFSFindNext+0x8ca/0x14c0
cifs_readdir+0xf51/0x29c0
iterate_dir+0x1c0/0x570
__x64_sys_getdents64+0x133/0x270
do_syscall_64+0x109/0x5d0
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
Allocated by task 83 on cpu 1 at 13.497119s:
cifs_buf_get+0x36/0x90
smb_init+0x4f/0x110
CIFSFindNext+0xf7/0x14c0
cifs_readdir+0xf51/0x29c0
Freed by task 83 on cpu 0 at 13.584018s:
cifs_buf_release+0x41/0x80
CIFSFindNext+0xfce/0x14c0
cifs_readdir+0xf51/0x29c0
The buggy address is located 16280 bytes inside of
freed 16588-byte region [ffff88807c820000, ffff88807c8240cc)
==================================================================
The same memcpy() first reads past the end of that object while it is
still live, a slab-out-of-bounds read that the following patches
bound; that is the taint the report above carries.
SMB1 is not negotiated by default; reaching this code requires an
explicit vers=1.0 mount.
Clear presume_name and resume_name_len whenever a new response is
installed and when the rewind path releases the search buffer, so that
the name never outlives the buffer it points into, and reset
resume_key with them, since it was taken from the same entry and would
otherwise be sent with an empty name. A response without a usable
last entry then continues the search with an empty resume name rather
than a stale one; CIFSFindNext() skips the copy of a zero-length name
so that it never runs on the NULL pointer.
The next patch in the series leaves last_entry NULL for a response
that carries no entries, and bounds LastNameOffset against the
received response rather than against CIFSMaxBufSize. Responses that
are given a last entry today then take the path fixed here, so that
patch must not be applied without this one.
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Fixes: b77d753c413e ("[CIFS] Check that last search entry resume key is valid")
Cc: stable@vger.kernel.org
Assisted-by: Bynario AI
Signed-off-by: Diego Oliva <diego@bynar.io>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/cifs/cifssmb.c | 11 ++++++++++-
fs/cifs/readdir.c | 3 +++
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/fs/cifs/cifssmb.c b/fs/cifs/cifssmb.c
index 5b1fb3216f238..6dc0b1793cbc7 100644
--- a/fs/cifs/cifssmb.c
+++ b/fs/cifs/cifssmb.c
@@ -4465,6 +4465,9 @@ CIFSFindFirst(const unsigned int xid, struct cifs_tcon *tcon,
psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
psrch_inf->index_of_last_entry = 2 /* skip . and .. */ +
psrch_inf->entries_in_buffer;
+ psrch_inf->presume_name = NULL;
+ psrch_inf->resume_name_len = 0;
+ psrch_inf->resume_key = 0;
lnoff = le16_to_cpu(parms->LastNameOffset);
if (CIFSMaxBufSize < lnoff) {
cifs_dbg(VFS, "ignoring corrupt resume name\n");
@@ -4528,7 +4531,10 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
name_len = psrch_inf->resume_name_len;
params += name_len;
if (name_len < PATH_MAX) {
- memcpy(pSMB->ResumeFileName, psrch_inf->presume_name, name_len);
+ if (name_len) {
+ memcpy(pSMB->ResumeFileName,
+ psrch_inf->presume_name, name_len);
+ }
byte_count += name_len;
/* 14 byte parm len above enough for 2 byte null terminator */
pSMB->ResumeFileName[name_len] = 0;
@@ -4583,6 +4589,9 @@ int CIFSFindNext(const unsigned int xid, struct cifs_tcon *tcon,
psrch_inf->endOfSearch = !!parms->EndofSearch;
psrch_inf->entries_in_buffer = le16_to_cpu(parms->SearchCount);
psrch_inf->index_of_last_entry += psrch_inf->entries_in_buffer;
+ psrch_inf->presume_name = NULL;
+ psrch_inf->resume_name_len = 0;
+ psrch_inf->resume_key = 0;
lnoff = le16_to_cpu(parms->LastNameOffset);
if (CIFSMaxBufSize < lnoff) {
cifs_dbg(VFS, "ignoring corrupt resume name\n");
diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 7c47a03afbcc3..cf099fce9ba1a 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -766,6 +766,9 @@ find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
cfile->srch_inf.ntwrk_buf_start = NULL;
cfile->srch_inf.srch_entries_start = NULL;
cfile->srch_inf.last_entry = NULL;
+ cfile->srch_inf.presume_name = NULL;
+ cfile->srch_inf.resume_name_len = 0;
+ cfile->srch_inf.resume_key = 0;
}
rc = initiate_cifs_search(xid, file, full_path);
if (rc) {
--
2.53.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-11-04 19:45 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-11-04 13:36 FAILED: patch "[PATCH] smb: client: fix use-after-free infoleak via the readdir" failed to apply to 5.15-stable tree gregkh
2026-11-04 19:45 ` [PATCH 5.15.y 1/3] smb: client: fix warning in CIFSFindFirst() Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 2/3] smb: client: fix warning in CIFSFindNext() Sasha Levin
2026-11-04 19:45 ` [PATCH 5.15.y 3/3] smb: client: fix use-after-free infoleak via the readdir resume name Sasha Levin
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