6.12-stable review patch. If anyone has any objections, please let me know.
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From: Alan Stern stern@rowland.harvard.edu
[ Upstream commit a6b87bfc2ab5bccb7ad953693c85d9062aef3fdd ]
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.c... 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.harvar... Signed-off-by: Benjamin Tissoires bentiss@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hid/hid-core.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c index 5169d8d56c889..9910c6d3fef30 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);