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[PATCH 4.19.y 8/9] loop: Check for overflow while configuring loop

by Genjian

From: Siddh Raman Pant <code(a)siddh.me> [ Upstream commit c490a0b5a4f36da3918181a8acdc6991d967c5f3 ] The userspace can configure a loop using an ioctl call, wherein a configuration of type loop_config is passed (see lo_ioctl()'s case on line 1550 of drivers/block/loop.c). This proceeds to call loop_configure() which in turn calls loop_set_status_from_info() (see line 1050 of loop.c), passing &config->info which is of type loop_info64*. This function then sets the appropriate values, like the offset. loop_device has lo_offset of type loff_t (see line 52 of loop.c), which is typdef-chained to long long, whereas loop_info64 has lo_offset of type __u64 (see line 56 of include/uapi/linux/loop.h). The function directly copies offset from info to the device as follows (See line 980 of loop.c): lo->lo_offset = info->lo_offset; This results in an overflow, which triggers a warning in iomap_iter() due to a call to iomap_iter_done() which has: WARN_ON_ONCE(iter->iomap.offset > iter->pos); Thus, check for negative value during loop_set_status_from_info(). Bug report: https://syzkaller.appspot.com/bug?id=c620fe14aac810396d3c3edc9ad73848bf69a2… Reported-and-tested-by: syzbot+a8e049cd3abd342936b6(a)syzkaller.appspotmail.com Cc: stable(a)vger.kernel.org Reviewed-by: Matthew Wilcox (Oracle) <willy(a)infradead.org> Signed-off-by: Siddh Raman Pant <code(a)siddh.me> Reviewed-by: Christoph Hellwig <hch(a)lst.de> Link: https://lore.kernel.org/r/20220823160810.181275-1-code@siddh.me Signed-off-by: Jens Axboe <axboe(a)kernel.dk> Signed-off-by: Genjian Zhang <zhanggenjian(a)kylinos.cn> --- drivers/block/loop.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 0fefd21f0c71..c1caa3e2355f 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -1271,6 +1271,11 @@ loop_set_status_from_info(struct loop_device *lo, lo->lo_offset = info->lo_offset; lo->lo_sizelimit = info->lo_sizelimit; + + /* loff_t vars have been assigned __u64 */ + if (lo->lo_offset < 0 || lo->lo_sizelimit < 0) + return -EOVERFLOW; + memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE); memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE); lo->lo_file_name[LO_NAME_SIZE-1] = 0; -- 2.25.1

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