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authorDaniel Axtens <dja@axtens.net>2020-06-04 16:51:27 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-04 19:06:26 -0700
commit54e200ab40fc14c863bcc80a51e20b7906608fce (patch)
treedef27b899efd5627cd2e739ea5ca3be2a7c2c1a5 /kernel/relay.c
parent67446283d89467edae5ad9f632ee31f0fbae35fe (diff)
kernel/relay.c: handle alloc_percpu returning NULL in relay_open
alloc_percpu() may return NULL, which means chan->buf may be set to NULL. In that case, when we do *per_cpu_ptr(chan->buf, ...), we dereference an invalid pointer: BUG: Unable to handle kernel data access at 0x7dae0000 Faulting instruction address: 0xc0000000003f3fec ... NIP relay_open+0x29c/0x600 LR relay_open+0x270/0x600 Call Trace: relay_open+0x264/0x600 (unreliable) __blk_trace_setup+0x254/0x600 blk_trace_setup+0x68/0xa0 sg_ioctl+0x7bc/0x2e80 do_vfs_ioctl+0x13c/0x1300 ksys_ioctl+0x94/0x130 sys_ioctl+0x48/0xb0 system_call+0x5c/0x68 Check if alloc_percpu returns NULL. This was found by syzkaller both on x86 and powerpc, and the reproducer it found on powerpc is capable of hitting the issue as an unprivileged user. Fixes: 017c59c042d0 ("relay: Use per CPU constructs for the relay channel buffer pointers") Reported-by: syzbot+1e925b4b836afe85a1c6@syzkaller-ppc64.appspotmail.com Reported-by: syzbot+587b2421926808309d21@syzkaller-ppc64.appspotmail.com Reported-by: syzbot+58320b7171734bf79d26@syzkaller.appspotmail.com Reported-by: syzbot+d6074fb08bdb2e010520@syzkaller.appspotmail.com Signed-off-by: Daniel Axtens <dja@axtens.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Reviewed-by: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com> Acked-by: David Rientjes <rientjes@google.com> Cc: Akash Goel <akash.goel@intel.com> Cc: Andrew Donnellan <ajd@linux.ibm.com> Cc: Guenter Roeck <linux@roeck-us.net> Cc: Salvatore Bonaccorso <carnil@debian.org> Cc: <stable@vger.kernel.org> [4.10+] Link: http://lkml.kernel.org/r/20191219121256.26480-1-dja@axtens.net Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/relay.c')
-rw-r--r--kernel/relay.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/kernel/relay.c b/kernel/relay.c
index 90c7a002436d..dc82705e1cff 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -581,6 +581,11 @@ struct rchan *relay_open(const char *base_filename,
return NULL;
chan->buf = alloc_percpu(struct rchan_buf *);
+ if (!chan->buf) {
+ kfree(chan);
+ return NULL;
+ }
+
chan->version = RELAYFS_CHANNEL_VERSION;
chan->n_subbufs = n_subbufs;
chan->subbuf_size = subbuf_size;