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9p/net: fix improper handling of bogus negative read/write replies

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[ Upstream commit d0259a856afca31d699b706ed5e2adf11086c73b ]

In p9_client_write() and p9_client_read_once(), if the server
incorrectly replies with success but a negative write/read count then we
would consider written (negative) <= rsize (positive) because both
variables were signed.

Make variables unsigned to avoid this problem.

The reproducer linked below now fails with the following error instead
of a null pointer deref:
9pnet: bogus RWRITE count (4294967295 > 3)

Reported-by: Robert Morris <rtm@mit.edu>
Closes: https://lore.kernel.org/16271.1734448631@26-5-164.dynamic.csail.mit.edu
Message-ID: <20250319-9p_unsigned_rw-v3-1-71327f1503d0@codewreck.org>
Reviewed-by: Christian Schoenebeck <linux_oss@crudebyte.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Dominique Martinet 2025-03-19 20:20:15 +09:00 committed by Greg Kroah-Hartman
parent 43b498a845
commit 468ff4a7c6
1 changed files with 16 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
net/9p/client.c
View File

@ -1545,7 +1545,8 @@ p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
struct p9_client *clnt = fid->clnt;
struct p9_req_t *req;
int count = iov_iter_count(to);
int rsize, received, non_zc = 0;
u32 rsize, received;
bool non_zc = false;
char *dataptr;
*err = 0;
@ -1568,7 +1569,7 @@ p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
0, 11, "dqd", fid->fid,
offset, rsize);
} else {
non_zc = 1;
non_zc = true;
req = p9_client_rpc(clnt, P9_TREAD, "dqd", fid->fid, offset,
rsize);
}
@ -1589,11 +1590,11 @@ p9_client_read_once(struct p9_fid *fid, u64 offset, struct iov_iter *to,
return 0;
}
if (rsize < received) {
pr_err("bogus RREAD count (%d > %d)\n", received, rsize);
pr_err("bogus RREAD count (%u > %u)\n", received, rsize);
received = rsize;
}
p9_debug(P9_DEBUG_9P, "<<< RREAD count %d\n", received);
p9_debug(P9_DEBUG_9P, "<<< RREAD count %u\n", received);
if (non_zc) {
int n = copy_to_iter(dataptr, received, to);
@ -1620,9 +1621,9 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
*err = 0;
while (iov_iter_count(from)) {
int count = iov_iter_count(from);
int rsize = fid->iounit;
int written;
size_t count = iov_iter_count(from);
u32 rsize = fid->iounit;
u32 written;
if (!rsize || rsize > clnt->msize - P9_IOHDRSZ)
rsize = clnt->msize - P9_IOHDRSZ;
@ -1630,7 +1631,7 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
if (count < rsize)
rsize = count;
p9_debug(P9_DEBUG_9P, ">>> TWRITE fid %d offset %llu count %d (/%d)\n",
p9_debug(P9_DEBUG_9P, ">>> TWRITE fid %d offset %llu count %u (/%zu)\n",
fid->fid, offset, rsize, count);
/* Don't bother zerocopy for small IO (< 1024) */
@ -1656,11 +1657,11 @@ p9_client_write(struct p9_fid *fid, u64 offset, struct iov_iter *from, int *err)
break;
}
if (rsize < written) {
pr_err("bogus RWRITE count (%d > %d)\n", written, rsize);
pr_err("bogus RWRITE count (%u > %u)\n", written, rsize);
written = rsize;
}
p9_debug(P9_DEBUG_9P, "<<< RWRITE count %d\n", written);
p9_debug(P9_DEBUG_9P, "<<< RWRITE count %u\n", written);
p9_req_put(clnt, req);
iov_iter_revert(from, count - written - iov_iter_count(from));
@ -2056,7 +2057,8 @@ EXPORT_SYMBOL_GPL(p9_client_xattrcreate);
int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
{
int err, rsize, non_zc = 0;
int err, non_zc = 0;
u32 rsize;
struct p9_client *clnt;
struct p9_req_t *req;
char *dataptr;
@ -2065,7 +2067,7 @@ int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
iov_iter_kvec(&to, ITER_DEST, &kv, 1, count);
p9_debug(P9_DEBUG_9P, ">>> TREADDIR fid %d offset %llu count %d\n",
p9_debug(P9_DEBUG_9P, ">>> TREADDIR fid %d offset %llu count %u\n",
fid->fid, offset, count);
err = 0;
@ -2101,11 +2103,11 @@ int p9_client_readdir(struct p9_fid *fid, char *data, u32 count, u64 offset)
goto free_and_error;
}
if (rsize < count) {
pr_err("bogus RREADDIR count (%d > %d)\n", count, rsize);
pr_err("bogus RREADDIR count (%u > %u)\n", count, rsize);
count = rsize;
}
p9_debug(P9_DEBUG_9P, "<<< RREADDIR count %d\n", count);
p9_debug(P9_DEBUG_9P, "<<< RREADDIR count %u\n", count);
if (non_zc)
memmove(data, dataptr, count);