4.17-stable review patch. If anyone has any objections, please let me know.
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From: Dave Wysochanski dwysocha@redhat.com
commit d68894800ec5712d7ddf042356f11e36f87d7f78 upstream.
In nfs_idmap_read_and_verify_message there is an incorrect sprintf '%d' that converts the __u32 'im_id' from struct idmap_msg to 'id_str', which is a stack char array variable of length NFS_UINT_MAXLEN == 11. If a uid or gid value is > 2147483647 = 0x7fffffff, the conversion overflows into a negative value, for example: crash> p (unsigned) (0x80000000) $1 = 2147483648 crash> p (signed) (0x80000000) $2 = -2147483648 The '-' sign is written to the buffer and this causes a 1 byte overflow when the NULL byte is written, which corrupts kernel stack memory. If CONFIG_CC_STACKPROTECTOR_STRONG is set we see a stack-protector panic:
[11558053.616565] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: ffffffffa05b8a8c [11558053.639063] CPU: 6 PID: 9423 Comm: rpc.idmapd Tainted: G W ------------ T 3.10.0-514.el7.x86_64 #1 [11558053.641990] Hardware name: Red Hat OpenStack Compute, BIOS 1.10.2-3.el7_4.1 04/01/2014 [11558053.644462] ffffffff818c7bc0 00000000b1f3aec1 ffff880de0f9bd48 ffffffff81685eac [11558053.646430] ffff880de0f9bdc8 ffffffff8167f2b3 ffffffff00000010 ffff880de0f9bdd8 [11558053.648313] ffff880de0f9bd78 00000000b1f3aec1 ffffffff811dcb03 ffffffffa05b8a8c [11558053.650107] Call Trace: [11558053.651347] [<ffffffff81685eac>] dump_stack+0x19/0x1b [11558053.653013] [<ffffffff8167f2b3>] panic+0xe3/0x1f2 [11558053.666240] [<ffffffff811dcb03>] ? kfree+0x103/0x140 [11558053.682589] [<ffffffffa05b8a8c>] ? idmap_pipe_downcall+0x1cc/0x1e0 [nfsv4] [11558053.689710] [<ffffffff810855db>] __stack_chk_fail+0x1b/0x30 [11558053.691619] [<ffffffffa05b8a8c>] idmap_pipe_downcall+0x1cc/0x1e0 [nfsv4] [11558053.693867] [<ffffffffa00209d6>] rpc_pipe_write+0x56/0x70 [sunrpc] [11558053.695763] [<ffffffff811fe12d>] vfs_write+0xbd/0x1e0 [11558053.702236] [<ffffffff810acccc>] ? task_work_run+0xac/0xe0 [11558053.704215] [<ffffffff811fec4f>] SyS_write+0x7f/0xe0 [11558053.709674] [<ffffffff816964c9>] system_call_fastpath+0x16/0x1b
Fix this by calling the internally defined nfs_map_numeric_to_string() function which properly uses '%u' to convert this __u32. For consistency, also replace the one other place where snprintf is called.
Signed-off-by: Dave Wysochanski dwysocha@redhat.com Reported-by: Stephen Johnston sjohnsto@redhat.com Fixes: cf4ab538f1516 ("NFSv4: Fix the string length returned by the idmapper") Cc: stable@vger.kernel.org # v3.4+ Signed-off-by: Trond Myklebust trond.myklebust@hammerspace.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/nfs/nfs4idmap.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
--- a/fs/nfs/nfs4idmap.c +++ b/fs/nfs/nfs4idmap.c @@ -343,7 +343,7 @@ static ssize_t nfs_idmap_lookup_name(__u int id_len; ssize_t ret;
- id_len = snprintf(id_str, sizeof(id_str), "%u", id); + id_len = nfs_map_numeric_to_string(id, id_str, sizeof(id_str)); ret = nfs_idmap_get_key(id_str, id_len, type, buf, buflen, idmap); if (ret < 0) return -EINVAL; @@ -627,7 +627,8 @@ static int nfs_idmap_read_and_verify_mes if (strcmp(upcall->im_name, im->im_name) != 0) break; /* Note: here we store the NUL terminator too */ - len = sprintf(id_str, "%d", im->im_id) + 1; + len = 1 + nfs_map_numeric_to_string(im->im_id, id_str, + sizeof(id_str)); ret = nfs_idmap_instantiate(key, authkey, id_str, len); break; case IDMAP_CONV_IDTONAME: