diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2025-07-23 10:37:04 -0400 |
|---|---|---|
| committer | Benjamin Tissoires <bentiss@kernel.org> | 2025-07-25 13:45:25 +0200 |
| commit | a6b87bfc2ab5bccb7ad953693c85d9062aef3fdd (patch) | |
| tree | d6a04b6df6860716cf58ee1480ada22c0875fcdc | |
| parent | 12f33ef6c2aaa410b7ccf039289fe2b04ab2252f (diff) | |
HID: core: Harden s32ton() against conversion to 0 bits
Testing by the syzbot fuzzer showed that the HID core gets a
shift-out-of-bounds exception when it tries to convert a 32-bit
quantity to a 0-bit quantity. Ideally this should never occur, but
there are buggy devices and some might have a report field with size
set to zero; we shouldn't reject the report or the device just because
of that.
Instead, harden the s32ton() routine so that it returns a reasonable
result instead of crashing when it is called with the number of bits
set to 0 -- the same as what snto32() does.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-usb/68753a08.050a0220.33d347.0008.GAE@google.com/
Tested-by: syzbot+b63d677d63bcac06cf90@syzkaller.appspotmail.com
Fixes: dde5845a529f ("[PATCH] Generic HID layer - code split")
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/613a66cd-4309-4bce-a4f7-2905f9bce0c9@rowland.harvard.edu
Signed-off-by: Benjamin Tissoires <bentiss@kernel.org>
| -rw-r--r-- | drivers/hid/hid-core.c | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index ef1f79951d9b..f7d4efcae603 100644 --- a/drivers/hid/hid-core.c +++ b/drivers/hid/hid-core.c @@ -66,8 +66,12 @@ static s32 snto32(__u32 value, unsigned int n) static u32 s32ton(__s32 value, unsigned int n) { - s32 a = value >> (n - 1); + s32 a; + if (!value || !n) + return 0; + + a = value >> (n - 1); if (a && a != -1) return value < 0 ? 1 << (n - 1) : (1 << (n - 1)) - 1; return value & ((1 << n) - 1); |