| Message ID | 20241222-9p_unsigned_rw-v1-1-3ea971d200cb@codewreck.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | 9p/net: fix improper handling of bogus negative read/write replies | expand |
On Sunday, December 22, 2024 2:57:48 PM CET Dominique Martinet wrote: > 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 > Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> > --- > net/9p/client.c | 28 +++++++++++++++------------- > 1 file changed, 15 insertions(+), 13 deletions(-) > > diff --git a/net/9p/client.c b/net/9p/client.c > index 09f8ced9f8bb..c290d96e1bb3 100644 > --- a/net/9p/client.c > +++ b/net/9p/client.c > @@ -1548,7 +1548,8 @@ 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; > @@ -1571,7 +1572,7 @@ 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); > } > @@ -1592,11 +1593,11 @@ 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; Does `received = rsize` make sense here? I would rather do `received = 0` to prevent copying garbage below, that would be ignored by caller on error case anyway. > } > > - 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); > @@ -1623,9 +1624,9 @@ 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); > + size_t rsize = fid->iounit; I think that would break 64-bit big-endian systems, as `rsize` is passed via format below as "d" (32-bit) type. > + u32 written; > > if (!rsize || rsize > clnt->msize - P9_IOHDRSZ) > rsize = clnt->msize - P9_IOHDRSZ; > @@ -1633,7 +1634,7 @@ 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 %zu (/%zu)\n", > fid->fid, offset, rsize, count); > > /* Don't bother zerocopy for small IO (< 1024) */ > @@ -1659,11 +1660,11 @@ 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 > %zu)\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)); > @@ -2098,7 +2099,8 @@ 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; > @@ -2142,11 +2144,11 @@ 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); > > --- > base-commit: cdd30ebb1b9f36159d66f088b61aee264e649d7a > change-id: 20241222-9p_unsigned_rw-03f95da525a0 > > Best regards, >
diff --git a/net/9p/client.c b/net/9p/client.c index 09f8ced9f8bb..c290d96e1bb3 100644 --- a/net/9p/client.c +++ b/net/9p/client.c @@ -1548,7 +1548,8 @@ 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; @@ -1571,7 +1572,7 @@ 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); } @@ -1592,11 +1593,11 @@ 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); @@ -1623,9 +1624,9 @@ 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); + size_t rsize = fid->iounit; + u32 written; if (!rsize || rsize > clnt->msize - P9_IOHDRSZ) rsize = clnt->msize - P9_IOHDRSZ; @@ -1633,7 +1634,7 @@ 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 %zu (/%zu)\n", fid->fid, offset, rsize, count); /* Don't bother zerocopy for small IO (< 1024) */ @@ -1659,11 +1660,11 @@ 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 > %zu)\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)); @@ -2098,7 +2099,8 @@ 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; @@ -2142,11 +2144,11 @@ 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);
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 Signed-off-by: Dominique Martinet <asmadeus@codewreck.org> --- net/9p/client.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) --- base-commit: cdd30ebb1b9f36159d66f088b61aee264e649d7a change-id: 20241222-9p_unsigned_rw-03f95da525a0 Best regards,