6.5-stable review patch. If anyone has any objections, please let me know.
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From: David Howells dhowells@redhat.com
commit 37de5a80e932f828c34abeaae63170d73930dca3 upstream.
Each smb_rqst struct contains two things: an array of kvecs (rq_iov) that contains the protocol data for an RPC op and an iterator (rq_iter) that contains the data payload of an RPC op. When an smb_rqst is allocated rq_iter is it always cleared, but we don't set it up unless we're going to use it.
The functions that determines the size of the ciphertext buffer that will be needed to encrypt a request, cifs_get_num_sgs(), assumes that rq_iter is always initialised - and employs user_backed_iter() to check that the iterator isn't user-backed. This used to incidentally work, because ->user_backed was set to false because the iterator has never been initialised, but with commit f1b4cb650b9a0eeba206d8f069fcdc532bfbcd74[1] which changes user_backed_iter() to determine this based on the iterator type insted, a warning is now emitted:
WARNING: CPU: 7 PID: 4584 at fs/smb/client/cifsglob.h:2165 smb2_get_aead_req+0x3fc/0x420 [cifs] ... RIP: 0010:smb2_get_aead_req+0x3fc/0x420 [cifs] ... crypt_message+0x33e/0x550 [cifs] smb3_init_transform_rq+0x27d/0x3f0 [cifs] smb_send_rqst+0xc7/0x160 [cifs] compound_send_recv+0x3ca/0x9f0 [cifs] cifs_send_recv+0x25/0x30 [cifs] SMB2_tcon+0x38a/0x820 [cifs] cifs_get_smb_ses+0x69c/0xee0 [cifs] cifs_mount_get_session+0x76/0x1d0 [cifs] dfs_mount_share+0x74/0x9d0 [cifs] cifs_mount+0x6e/0x2e0 [cifs] cifs_smb3_do_mount+0x143/0x300 [cifs] smb3_get_tree+0x15e/0x290 [cifs] vfs_get_tree+0x2d/0xe0 do_new_mount+0x124/0x340 __se_sys_mount+0x143/0x1a0
The problem is that rq_iter was never set, so the type is 0 (ie. ITER_UBUF) which causes user_backed_iter() to return true. The code doesn't malfunction because it checks the size of the iterator - which is 0.
Fix cifs_get_num_sgs() to ignore rq_iter if its count is 0, thereby bypassing the warnings.
It might be better to explicitly initialise rq_iter to a zero-length ITER_BVEC, say, as it can always be reinitialised later.
Fixes: d08089f649a0 ("cifs: Change the I/O paths to use an iterator rather than a page list") Reported-by: Damian Tometzki damian@riscv-rocks.de Closes: https://lore.kernel.org/r/ZUfQo47uo0p2ZsYg@fedora.fritz.box/ Tested-by: Damian Tometzki damian@riscv-rocks.de Cc: stable@vger.kernel.org cc: Eric Biggers ebiggers@kernel.org cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... [1] Reviewed-by: Paulo Alcantara (SUSE) pc@manguebit.com Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: Steve French stfrench@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/smb/client/cifsglob.h | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-)
--- a/fs/smb/client/cifsglob.h +++ b/fs/smb/client/cifsglob.h @@ -2113,6 +2113,7 @@ static inline int cifs_get_num_sgs(const unsigned int len, skip; unsigned int nents = 0; unsigned long addr; + size_t data_size; int i, j;
/* @@ -2128,17 +2129,21 @@ static inline int cifs_get_num_sgs(const * rqst[1+].rq_iov[0+] data to be encrypted/decrypted */ for (i = 0; i < num_rqst; i++) { + data_size = iov_iter_count(&rqst[i].rq_iter); + /* We really don't want a mixture of pinned and unpinned pages * in the sglist. It's hard to keep track of which is what. * Instead, we convert to a BVEC-type iterator higher up. */ - if (WARN_ON_ONCE(user_backed_iter(&rqst[i].rq_iter))) + if (data_size && + WARN_ON_ONCE(user_backed_iter(&rqst[i].rq_iter))) return -EIO;
/* We also don't want to have any extra refs or pins to clean * up in the sglist. */ - if (WARN_ON_ONCE(iov_iter_extract_will_pin(&rqst[i].rq_iter))) + if (data_size && + WARN_ON_ONCE(iov_iter_extract_will_pin(&rqst[i].rq_iter))) return -EIO;
for (j = 0; j < rqst[i].rq_nvec; j++) { @@ -2154,7 +2159,8 @@ static inline int cifs_get_num_sgs(const } skip = 0; } - nents += iov_iter_npages(&rqst[i].rq_iter, INT_MAX); + if (data_size) + nents += iov_iter_npages(&rqst[i].rq_iter, INT_MAX); } nents += DIV_ROUND_UP(offset_in_page(sig) + SMB2_SIGNATURE_SIZE, PAGE_SIZE); return nents;